Methods and compositions relating to anti-il-21 receptor antibodies

ABSTRACT

The present invention provides compositions and methods relating to antigen binding proteins against IL-21 receptor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/715,156, filed Oct. 17, 2012, which is incorporated herein byreference in its entirety.

REFERENCE TO THE SEQUENCE LISTING

The present application is being filed along with a Sequence Listing inelectronic format via EFS-Web. The Sequence Listing is provided as atext file entitled A1731USNPst25.txt, created Mar. 14, 2013, which is238,880 bytes in size. The information in the electronic format of theSequence Listing is incorporated herein by reference in its entirety.

BACKGROUND

The cytokine IL-21 signals through a heterodimeric receptor consistingof the common gamma chain and IL-21-specific receptor called “IL-21receptor” or “IL-21R.” IL-21 receptor is expressed on a number of typesof cells of the immune system, including dendritic cells, macrophages,NK cells, B cells, and CD4+ CD8+ T cells. With respect to T cells, IL-21signaling stimulates CD8+ T cell proliferation and expansion. It causesnaïve T cells to differentiate into Th17 cells, which it stabilizes andmaintains. IL-21 signaling also down-regulates induced regulatory Tcells and inhibits the suppressive effects of Tregs. Pathologicautoantibodies can be produced in germinal centers, the formation ofwhich depends on IL-21 signaling. IL-21 also affects B cell activationplasma cell differentiation.

IL-21 signaling is associated with several pathologic conditions.Elevated levels of IL-21 are found in the sera of systemic lupuserythematosus (SLE) patients. Polymorphisms in IL-21 and IL-21 receptorhave been implicated in increased susceptibility to developing SLE.Mouse models of SLE further implicate a role for IL-21 signaling.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an isolated anti-IL-21receptor antigen binding protein, wherein said antigen binding proteincomprises either the light chain variable domain sequence of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; theheavy chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; the heavy chain variabledomain and the light chain variable domain of antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a light chainvariable domain sequence that is at least 90%, 95%, 97%, or 99%identical to the light chain variable domain sequence of antibody 10C2,8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a heavy chainvariable domain sequence that is at least 90%, 95%, 97%, or 99%identical to the heavy chain variable domain sequence of antibody 10C2,8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a light chainvariable domain sequence and a heavy chain variable domain sequence thateach is at least 90%, 95%, 97%, or 99% identical to the light chainvariable domain sequence and the heavy chain variable domain sequence,respectively, of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3; a light chain variable domain sequence that differsat no more than 15, 12, 10, 8, 5, or 3 amino acid positions from thelight chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a heavy chain variabledomain sequence that differs at no more than 15, 12, 10, 8, 5, or 3amino acid positions from the heavy chain variable domain sequence ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3;a light chain variable domain sequence and a heavy chain variable domainsequence that each differs at no more than 15, 12, 10, 8, 5, or 3 aminoacid positions from the light chain variable domain sequence and theheavy chain variable domain sequence, respectively, of antibody 10C2,8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a light chainvariable domain sequence that is encoded by a nucleic acid sequence thatis at least 90%, 95%, 97%, or 99% identical to the nucleic acid sequenceencoding the light chain variable domain sequence of antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 as provided in FIG.5; a heavy chain variable domain sequence that is encoded by a nucleicacid sequence that is at least 90%, 95%, 97%, or 99% identical to thenucleic acid sequence encoding the heavy chain variable domain sequenceof antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or37G3, as provided in FIG. 3; a light chain variable domain sequence thatis encoded by a nucleic acid sequence that is at least 90%, 95%, 97%, or99% identical to the nucleic acid sequence encoding the light chainvariable domain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3, as provided in FIG. 5, and a heavychain variable domain sequence that is encoded by a nucleic acidsequence that is at least 90%, 95%, 97%, or 99% identical to the nucleicacid sequence encoding the heavy chain variable domain sequence of thesame antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or37G3, as provided in FIG. 3; a light chain variable domain sequence thatis encoded by a nucleic acid sequence that hybridizes under moderatelystringent, stringent, or highly stringent conditions to the nucleic acidsequence encoding the light chain variable domain sequence of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 asprovided in FIG. 5; a heavy chain variable domain sequence that isencoded by a nucleic acid sequence that hybridizes under moderatelystringent, stringent, or highly stringent conditions to the nucleic acidsequence encoding the heavy chain variable domain sequence of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 asprovided in FIG. 3; a light chain variable domain sequence that isencoded by a nucleic acid sequence that hybridizes under moderatelystringent, stringent, or highly stringent conditions to the nucleic acidsequence encoding the light chain variable domain sequence of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, asprovided in FIG. 5, and a heavy chain variable domain sequence that isencoded by a nucleic acid sequence that hybridizes under moderatelystringent, stringent, or highly stringent conditions to the nucleic acidsequence encoding the heavy chain variable domain sequence of the sameantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3,as provided in FIG. 3; CDR1, CDR2, and CDR3 of the light chain variabledomain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3; CDR1, CDR2, and CDR3 of the light chain variabledomain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3; CDR1, CDR2, and CDR3 of the light chain variabledomain sequence, and CDR1, CDR2, and CDR3 of the heavy chain variabledomain sequence, of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3; light chain variable domain CDR1, CDR2, and CDR3sequences that each differs at no more than 3, 2, or 1 amino acidpositions from the light chain variable domain CDR1, CDR2, and CDR3sequences, respectively, of the light chain variable domain sequence ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3;heavy chain variable domain CDR1, CDR2, and CDR3 sequences that eachdiffers at no more than 3, 2, or 1 amino acid positions from the heavychain variable domain CDR1, CDR2, and CDR3 sequences, respectively, ofthe heavy chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or light chain variabledomain CDR1, CDR2, and CDR3 sequences that each differs at no more than3, 2, or 1 amino acid positions from the light chain variable domainCDR1, CDR2, and CDR3 sequences, respectively, of the light chainvariable domain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3, and heavy chain variable domain CDR1,CDR2, and CDR3 sequences that each differs at no more than 3, 2, or 1amino acid positions from the heavy chain variable domain CDR1, CDR2,and CDR3 sequences, respectively, of the heavy chain variable domainsequence of the same antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3.

In one embodiment, the anti-IL-21 receptor antigen binding proteincomprises: a heavy chain variable domain sequence disclosed in FIG. 2; alight chain variable domain sequence disclosed in FIG. 4; a heavy chainvariable domain sequence disclosed in FIG. 2 and a light chain variabledomain sequence disclosed in FIG. 4; the CDR1, CDR2, and CDR3 sequencesof a heavy chain sequence disclosed in FIG. 2; the CDR1, CDR2, and CDR3sequences of a light chain sequence disclosed in FIG. 4; the CDR1, CDR2,and CDR3 sequences of a heavy chain sequence disclosed in FIG. 2 and theCDR1, CDR2, and CDR3 sequences of a light chain sequence disclosed inFIG. 4; the heavy chain constant region disclosed in FIG. 7; the lambdalight chain constant region disclosed in FIG. 7; the kappa light chainconstant region disclosed in FIG. 7; the heavy chain constant regiondisclosed in FIG. 7 and either the lambda light constant regiondisclosed in FIG. 7 or the kappa light chain constant region disclosedin FIG. 7; a heavy chain sequence disclosed in FIG. 8; a light chainsequence disclosed in FIG. 9; a heavy chain sequence disclosed in FIG. 8and a light chain sequence disclosed in FIG. 9, wherein said heavy chainand said light chain sequence are from the same antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; a heavy chainsequence disclosed in FIG. 10; a light chain sequence disclosed in FIG.11; a heavy chain sequence disclosed in FIG. 10 and a light chainsequence disclosed in FIG. 11, wherein said heavy chain and said lightchain sequence are from the same antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3.

In another embodiment, the isolated anti-IL-21 receptor antigen bindingprotein competes for binding to a human IL-21 receptor with antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3.

In another embodiment, the isolated anti-IL-21 receptor antigen bindingprotein of claim 1, wherein said antigen binding protein compriseseither: a light chain variable domain that differs from the light chainvariable domain of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3 only in that one or more non-germline amino acidresidues are replaced with the corresponding germline residues; a heavychain variable domain that differs from the heavy chain variable domainof antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or37G3 only in that one or more non-germline amino acid residues arereplaced with the corresponding germline residues; or a light chainvariable domain that differs from the light chain variable domain ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3only in that one or more non-germline amino acid residues are replacedwith the corresponding germline residues, and a heavy chain variabledomain that differs from the heavy chain variable domain of the sameantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3only in that one or more non-germline amino acid residues are replacedwith the corresponding germline residues.

In another embodiment, the antigen binding protein comprises: a humanantibody; a humanized antibody; a chimeric antibody; a monoclonalantibody; a polyclonal antibody; a recombinant antibody; anantigen-binding antibody fragment; a single chain antibody; a diabody; atriabody; a tetrabody; a Fab fragment; a F(ab′)2 fragment; a domainantibody; an IgD antibody; an IgE antibody; an IgM antibody; an IgG1antibody; an IgG2 antibody; an IgG3 antibody; an IgG4 antibody; or anIgG4 antibody having at least one mutation in a hinge region thatalleviates a tendency to form intra-H chain disulfide bond.

In another embodiment, the antigen binding protein inhibits binding ofIL-21 to IL-21 receptor.

In another embodiment, the antigen binding protein shows activity in theB/T co-culture assay, the B cell IgA production assay, the CD8 IFN-γproduction assay, or the whole blood pSTAT3 stimulation assay, ofExample 3.

In another embodiment, the antigen binding protein has a potency aboutequal to or greater than the potency shown in Table 2 for antibodies34H7 or 29G8 in the B/T co-culture assay, the B cell IgA productionassay, the CD8 IFN-γ production assay, or the whole blood pSTAT3stimulation assay of Example 3.

In another aspect, the present invention provides an isolatedpolynucleotide comprising a sequence that encodes the light chain, theheavy chain, or both of one of the aforementioned anti-IL-21 receptorantigen binding proteins.

In one embodiment, the isolated polynucleotide comprises a light chainvariable domain nucleic acid sequence of FIG. 5 and/or a heavy chainvariable domain nucleic acid sequence of FIG. 3.

In another aspect, the present invention provides a plasmid comprisingan aforementioned isolated polynucleotide.

In one embodiment, the plasmid is an expression vector.

In another aspect, the present invention provides an isolated cellcomprising an aforementioned isolated polynucleotide.

In one embodiment, a chromosome of the cell comprises thepolynucleotide.

In another embodiment, the cell is a hybridoma.

In another embodiment, an expression vector comprises thepolynucleotide.

In another embodiment, the cell is a CHO cell.

In another embodiment, the cell is a bacterial cell.

In another embodiment, the cell is an E. coli cell.

In another embodiment, the cell is a yeast cell.

In another embodiment, the cell is an animal cell.

In another embodiment, the cell is a human cell.

In another aspect, the present invention provides a method of making ananti-IL-21 receptor antigen binding protein, comprising incubating anaforementioned isolated cell under conditions that allow it to expresssaid antigen binding protein.

In another aspect, the present invention provides a pharmaceuticalcomposition comprising an aforementioned anti-IL-21 receptor antigenbinding protein.

In another aspect, the present invention provides a method of treating acondition in a subject, comprising administering to said subject anaforementioned anti-IL-21 receptor antigen binding protein or theaforementioned pharmaceutical composition, wherein said condition istreated or prevented by a reduction in IL-21 receptor activity.

In one embodiment, about 15 milligrams to about 300 milligrams, about 30milligrams to about 200 milligrams, about 50 milligrams to about 150milligrams, or about 75 milligrams to about 125 milligrams of anaforementioned antigen binding protein is administered to the patient.

In another embodiment, administration of said antigen binding protein isrepeated three times per day, twice per day, once per day, once everytwo days, once every three days, once per week, twice per week, threetimes per week, four times per month, three times per month, twice permonth, once per month, once every two months, once every three months,once every four months, once every six months, or once per year.

In another embodiment, a dose and a frequency of administration of theantigen binding protein are used such as to maintain serum levels of theantigen binding protein in the patient at or above a desired level.

In another embodiment, the condition is an infectious, inflammatory, orautoimmune condition.

In another embodiment, the condition is Acquired Immune DeficiencySyndrome (AIDS), rheumatoid arthritis including juvenile rheumatoidarthritis, inflammatory bowel disease, ulcerative colitis, Crohn'sdisease, multiple sclerosis, Addison's disease, diabetes (type I),epididymitis, glomerulonephritis, Graves' disease, Guillain-Barresyndrome, Hashimoto's disease, hemolytic anemia, systemic lupuserythematosus (SLE), lupus nephritis, myasthenia gravis, pemphigus,psoriasis, psoriatic arthritis, atherosclerosis, erythropoietinresistance, graft versus host disease, transplant rejection, autoimmunehepatitis-induced hepatic injury, biliary cirrhosis, alcohol-inducedliver injury, alcoholic cirrhosis, rheumatic fever, sarcoidosis,scleroderma, Sjogren's syndrome, a spondyloarthropathy, ankylosingspondylitis, thyroiditis, vasculitis, atherosclerosis, coronary arterydisease, or heart disease.

In another embodiment, the method further comprises administering to thesubject a second treatment.

In another embodiment, the second treatment is an anti-inflammatory,anti-infectious disease, or anti-autoimmune disorder treatment.

In another embodiment, the antigen binding protein or pharmaceuticalcomposition is administered subcutaneously or intravenously.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A provides the amino acid sequence of human IL-21 receptor (SEQ IDNO: 5). FIG. 1B provides the amino acid sequence of murine IL-21receptor (SEQ ID NO: 6).

FIG. 2 provides amino acid sequences of the heavy chain variable domainsof anti-IL-21 receptor antibodies (SEQ ID NOS 7-16, respectively, inorder of appearance). CDR 1, 2, and 3 sequences (from left to right) areindicated in bold and underlined.

FIGS. 3A and B provide nucleic acid sequence encoding the heavy chainvariable domains of anti-IL-21 receptor (SEQ ID NOS 17-26, respectively,in order of appearance).

FIG. 4 provides amino acid sequences of the light chain variable domainsof anti-IL-21 receptor (SEQ ID NOS 27-36, respectively, in order ofappearance). CDR 1, 2, and 3 sequences (from left to right) areindicated in bold and underlined.

FIGS. 5A and B provide nucleic acid sequences encoding light chainvariable domains of anti-IL-21 receptor (SEQ ID NOS 37-46, respectively,in order of appearance).

FIG. 6 provides amino acid sequences for heavy and light chain CDRs ofanti-IL-21 receptor antibodies. Hyphens are numerical placeholders fornumbering purposes (Heavy chain CDR1 sequences disclosed as SEQ ID NOS47-48, 48-49, 49, 49, 49, 49-50, and 49, heavy chain CDR2 sequencesdisclosed as SEQ ID NOS 51-57, 56, 58 and 54, and heavy chain CDR3sequences disclosed as SEQ ID NOS 59-65, 64, 66 and 62, allrespectively, in order of appearance; Light chain CDR1 sequencesdisclosed as SEQ ID NOS 67-73, 72, 74 and 70, light chain CDR2 sequencesdisclosed as SEQ ID NOS 75-79, 79-80, 79, 81 and 78, and light chainCDR3 sequences disclosed as SEQ ID NOS 82-87, 87, 87-88 and 85, allrespectively, in order of appearance).

FIG. 7 provides amino acid and nucleic acid sequences for heavy andlight chain constant sequences (SEQ ID NOS 89-94, respectively, in orderof appearance).

FIGS. 8A and 8B provide amino acid sequences for heavy chain variabledomain and constant domain sequences for anti-IL-21 receptor antibodies(SEQ ID NOS 95-104, respectively, in order of appearance).

FIGS. 9A and 9B provide amino acid sequences for light chain variabledomain and constant domain sequences for anti-IL-21 receptor antibodies(SEQ ID NOS 105-114, respectively, in order of appearance).

FIGS. 10A and 10B provide amino acid sequences for signal sequences,heavy variable domain and constant domain sequences for anti-IL-21receptor antibodies (SEQ ID NOS 115-123, respectively, in order ofappearance).

FIGS. 11A and 11B provide amino acid sequences for signal sequences,light variable domain and constant domain sequences for anti-IL-21receptor antibodies (SEQ ID NOS 124-133, respectively, in order ofappearance).

FIGS. 12A-E provide heavy chain variable domain sequence groups (‘10C2Group’ sequences disclosed as SEQ ID NOS 7 and 134-140, ‘8B9 Group’sequences disclosed as SEQ ID NOS 8-9 and 141-160 , ‘29G8 Group’sequences disclosed as SEQ ID NOS 10 and 161-162, ‘31C5 Group’ sequencesdisclosed as SEQ ID NOS 11 and 163, ‘29G2 Group’ sequence disclosed asSEQ ID NO: 12, ‘31E7 Group’ sequences disclosed as SEQ ID NOS 13 and164-165, ‘34H7 Group’ sequences disclosed as SEQ ID NOS 14 and 166-171,‘30G3 Group’ sequence disclosed as SEQ ID NO: 15, and ‘37G3 Group’sequences disclosed as SEQ ID NOS 16 and 172-173, all respectively, inorder of appearance).

FIGS. 13A-C provide light chain variable domain sequence groups (‘10C2Group’ sequence disclosed as SEQ ID NO: 27, ‘8B9 Group’ sequencesdisclosed as SEQ ID NOS 28-29 and 174-177, ‘29G8 Group’ sequencesdisclosed as SEQ ID NOS 30 and 178, ‘31C5 Group’ sequence disclosed asSEQ ID NO: 31, ‘29G2 Group’ sequence disclosed as SEQ ID NO: 32, ‘31E7Group’ sequences disclosed as SEQ ID NOS 33 and 179-180, ‘34H7 Group’sequences disclosed as SEQ ID NOS 34 and 181-182, ‘30G3 Group’ sequencesdisclosed as SEQ ID NOS 35 and 183, and ‘37G3 Group’ sequences disclosedas SEQ ID NOS 36 and 184, all respectively, in order of appearance).

DETAILED DESCRIPTION

The section headings used herein are for organizational purposes onlyand are not to be construed as limiting the subject matter described.

Unless otherwise defined herein, scientific and technical terms used inconnection with the present application shall have the meanings that arecommonly understood by those of ordinary skill in the art. Further,unless otherwise required by context, singular terms shall includepluralities and plural terms shall include the singular.

Generally, the terminology and techniques of cell and tissue culture,molecular biology, immunology, microbiology, genetics, protein andnucleic acid chemistry, manufacturing, formulation, pharmacology, andmedicine described herein are those well known and commonly used in theart. The methods and techniques of the present application are generallyperformed according to conventional methods well known in the art and asdescribed in various general and more specific references that are citedand discussed throughout the present specification unless otherwiseindicated. See, e.g., Sambrook et al., Molecular Cloning: A LaboratoryManual, 3rd ed., Cold Spring Harbor Laboratory Press, Cold SpringHarbor, N.Y. (2001), Ausubel et al., Current Protocols in MolecularBiology, Greene Publishing Associates (1992), and Harlow and LaneAntibodies: A Laboratory Manual Cold Spring Harbor Laboratory Press,Cold Spring Harbor, N.Y. (1990), which are incorporated herein byreference. Enzymatic reactions and purification techniques are performedaccording to manufacturer's specifications, as commonly accomplished inthe art, or as described herein. The terminology used in connectionwith, and the laboratory procedures and techniques of, analyticalchemistry, synthetic organic chemistry, and medicinal and pharmaceuticalchemistry described herein are those well known and commonly used in theart. Standard techniques can be used for chemical syntheses, chemicalanalyses, pharmaceutical preparation, formulation, and delivery, andtreatment of patients.

This invention is not limited to the particular methodology, protocols,reagents, etc., described herein. The terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto limit the scope of the present invention as defined by the claims.

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients or reaction conditions usedherein should be understood as modified in all instances by the term“about” as that term would be interpreted by the person skilled in therelevant art.

DEFINITIONS

The term “polynucleotide” or “nucleic acid” includes nucleotide polymersof any length. They can be, for example, single-stranded,double-stranded, or triple-stranded, or a combination of single- and/ordouble- and/or triple-stranded. Where a nucleotide polymer comprisesmore than one strand, each strand is itself understood to be apolynucleotide or nucleic acid. Where a nucleotide polymer isdouble-stranded, typically each of the strands is complementary to theother, although their complementarity need not be perfect and in someinstances is sufficient to allow the stable association or hybridizationof the two strands only under certain hybridization conditions. Thenucleotides comprising the polynucleotide can be naturally-occurring orartificial nucleotide analogs, such as, for example, ribonucleotides,deoxyribonucleotides, or modified forms of either type of nucleotide, ora combination of different types of nucleotides and/or nucleotideanalogs. Said modifications include, for example, base modifications,such as bromouridine and inosine derivatives, ribose modifications, suchas 2′,3′-dideoxyribose, and internucleotide linkage modifications, suchas phosphorothioate, phosphorodithioate, phosphoroselenoate,phosphorodiselenoate, phosphoroanilothioate, phoshoraniladate andphosphoroamidate. The terms “polynucleotide” and “nucleic acid” includenucleotide polymers that have been covalently or non-covalently modifiedby the addition of one or more non-polynucleotide chemical entities,such as, for example, labels, (e.g., radiolabels), fluorescent labels,haptens or antigenic labels as well as nucleotide polymers that havebeen covalently or non-covalently bound to a solid object or surface,such as a hybridization membrane (e.g., a nitrocellulose hybridizationmembrane), a bead, a vessel wall, or the like.

The term “oligonucleotide” refers generally to shorter polynucleotide ornucleic acid sequences. The length of a particular oligonucleotide willdepend on how it is made and/or its intended use. Typically, it refersto a polynucleotide comprising 200 or fewer nucleotides. In someembodiments, oligonucleotides are 10 to 60 bases in length. In otherembodiments, oligonucleotides are 12, 13, 14, 15, 16, 17, 18, 19, or 20to 40 nucleotides in length. Oligonucleotides may be, for example,single-, double-, or triple-stranded. Single stranded oligonucleotidesmay be sense or antisense oligonucleotides. Oligonucleotides have manyuses, including, for example, as PCR primers, cloning primers, adaptersfor joining two or more polynucleotides, and hybridization probes.

An “isolated nucleic acid molecule” means a DNA or RNA of genomic, mRNA,cDNA, or synthetic origin, or some combination thereof, which is atleast partially removed from its natural environment. Examples ofisolated nucleic acid molecules include nucleic acids that havesequences found in nature but that are produced synthetically,naturally-occurring nucleic acids that are not associated with all or aportion of a polynucleotide in which the isolated polynucleotide isfound in nature, naturally-occurring nucleic acids that are linked to apolynucleotide to which they are not linked in nature, andnaturally-occurring nucleic acids that have been at least partiallyremoved from their natural cellular environment. For purposes of thisdisclosure, it should be understood that “a nucleic acid moleculecomprising” a particular nucleotide sequence does not encompass intactnaturally-occurring chromosomes. Isolated nucleic acid molecules“comprising” specified nucleic acid sequences may include othersequences as well, such as, for example, one or more other codingsequences, operably linked regulatory sequences that control or affectexpression of the coding region of the recited nucleic acid sequences,vector or plasmid sequences, sequences controlling or affectingreplication of the nucleic acid, restriction sites, primer bindingsites, and the like.

Unless specified otherwise, the left-hand end of any single-strandedpolynucleotide sequence provided herein is the 5′ end; the left-handdirection of double-stranded polynucleotide sequences is referred to asthe 5′ direction. The direction of 5′ to 3′ addition of nascent RNAtranscripts is referred to as the transcription direction; sequenceregions on the DNA strand having the same sequence as the RNA transcriptthat are 5′ to the 5′ end of the RNA transcript are referred to as“upstream sequences;” sequence regions on the DNA strand having the samesequence as the RNA transcript that are 3′ to the 3′ end of the RNAtranscript are referred to as “downstream sequences.”

The term “control sequence” refers to a polynucleotide sequence that canaffect the expression and/or processing of a coding sequence to which itis ligated. The nature of such control sequences may depend upon thehost organism. In particular embodiments, control sequences forprokaryotes may include a promoter, a ribosomal binding site, and atranscription termination sequence. Examples of control sequences foreukaryotes include promoters comprising one or a plurality ofrecognition sites for transcription factors, transcription enhancersequences, and transcription termination sequences. The term “controlsequences” can refer to leader sequences and/or fusion partner sequencesas well.

The term “vector” means any molecule or entity (e.g., nucleic acid,plasmid, bacteriophage or virus) used to transfer protein codinginformation into a host cell.

The terms “expression vector,” “expression plasmid,” and “expressionconstruct” each refers to a vector that is suitable for transformationof a host cell and contains nucleic acid sequences that allows (inconjunction with the host cell) expression of one or more heterologouscoding regions operatively linked thereto. An expression construct mayinclude, but is not limited to, sequences that affect or controltranscription, translation, and, if introns are present, affect RNAsplicing of a coding region operably linked thereto.

As used herein, “operably linked” means that the components to which theterm is applied are in a relationship that allows them to carry outtheir inherent or desired functions under suitable conditions. Anexample of a control sequence that is “operably linked” to a proteincoding sequence in a vector is an enhancer region that is ligated(either directly or via intermediary sequences) to the protein codingsequence such that expression of the protein coding sequence is achievedunder conditions compatible with the transcriptional activity of theenhancer region.

The term “host cell” means a cell capable of expressing, under thecorrect conditions, a coding sequence of interest. The term includes theprogeny of the parent cell, whether or not the progeny is identical inmorphology or in genetic make-up to the original parent cell, so long asthe coding sequence of interest is present. A “host cell” can be a cellthat has been transformed, or is capable of being transformed, with anucleic acid sequence and thereby express a coding sequence of interest.

The term “transduction” means the transfer of genes from one bacteriumto another, usually by bacteriophage. “Transduction” also refers to theacquisition and transfer of eukaryotic cellular sequences by replicationdefective retroviruses.

The term “transfection” means the uptake of foreign or exogenous DNA bya cell, and a cell has been “transfected” when the exogenous DNA hasbeen introduced into the cell. A number of transfection techniques arewell known in the art and are disclosed herein. See, e.g., Graham etal., 1973, Virology 52:456; Sambrook et al., 2001, Molecular Cloning: ALaboratory Manual, supra; Davis et al., 1986, Basic Methods in MolecularBiology, Elsevier; Chu et al., 1981, Gene 13:197. Such techniques can beused to introduce one or more exogenous DNA moieties into suitable hostcells. Depending on the technique used to make the transfected cell andthe desired use of the transfected cell, a cell can be transfectedeither stably or transiently.

The term “transformation” refers to a change in a cell's geneticcharacteristics, and a cell has been transformed when it has beenmodified to contain new DNA or RNA. For example, a cell is transformedwhere it is genetically modified from its native state by introducingnew genetic material via, for example, transfection or transduction, orvia another technique, such as a chemical, ballistic, or electroporationtechnique. Following transformation, the transforming DNA may recombinewith that of the cell by physically integrating into a chromosome of thecell, or may be maintained transiently as an episomal element withoutbeing replicated and/or stably propagated during cellular division, orit may replicate independently as a plasmid. A cell is considered tohave been “stably transformed” when the transforming DNA is replicatedas part of the host cell's cycle of cell division.

The terms “polypeptide” or “protein” are used interchangeably herein torefer to a polymer of amino acid residues. The terms also apply to aminoacid polymers in which one or more amino acid residues is an analog,derivative, or mimetic of a naturally occurring amino acid, as well asto naturally occurring amino acid polymers. The terms also encompassamino acid polymers that have been modified. Such modifications includeany naturally-occurring or artificial modification of a polypeptide.Some such modifications will alter the sequence of the polypeptide, butothers will not. Examples of such modifications include the addition ofcarbohydrate residues and phosphorylation. Polypeptides and proteins canbe produced and/or modified by a naturally-occurring and non-recombinantcell or they can be produced by a genetically-engineered or recombinantcell. “Polypeptides” and “proteins” comprise molecules having the aminoacid sequence of a native protein, or molecules having deletions from,additions to, and/or substitutions of one or more amino acids of, thenative sequence. The terms “polypeptide” and “protein” specificallyencompass IL-21 receptor antigen-binding proteins, antibodies, orsequences that have deletions from, additions to, and/or substitutionsof one or more amino acids of an antigen-binding protein. The term“polypeptide fragment” refers to a polypeptide that has anamino-terminal deletion, a carboxyl-terminal deletion, and/or aninternal deletion as compared with the full-length protein. Suchfragments may also contain modified amino acids as compared with thefull-length protein. In certain embodiments, fragments are about five to500 amino acids long. For example, fragments may be at least 5, 6, 8,10, 14, 20, 50, 70, 100, 110, 150, 200, 250, 300, 350, 400, or 450 aminoacids long. Useful polypeptide fragments include immunologicallyfunctional fragments of antibodies, including binding domains. In thecase of an IL-21 receptor-binding antibody, useful fragments include butare not limited to a CDR region, a variable domain of a heavy or lightchain, a portion of an antibody chain or just its variable regionincluding two CDRs, and the like.

An “isolated protein” (1) is free of at least some other proteins orcellular components with which it would normally be found, (2) isessentially free of other proteins from the same source, e.g., from thesame species, (3) is expressed by a cell from a different species, (4)has been separated from at least about 50 percent of polynucleotides,lipids, carbohydrates, or other materials with which it is associated innature, (5) is operably associated (by covalent or noncovalent bonds)with a polypeptide with which it is not associated in nature, or (6)does not occur in nature. An “isolated protein” can constitute at leastabout 5%, at least about 10%, at least about 25%, or at least about 50%of a given sample. Genomic DNA, cDNA, mRNA or other RNA, of syntheticorigin, or any combination thereof may encode such an isolated protein.In some embodiments, the isolated protein is substantially free fromproteins or polypeptides or other contaminants that are found in itsnatural environment that would interfere with its therapeutic,diagnostic, prophylactic, research or other use.

A “variant” of a polypeptide (e.g., of an antigen binding protein or ofan antibody) comprises an amino acid sequence wherein one or more aminoacid residues are inserted into, deleted from and/or substituted intothe amino acid sequence relative to another polypeptide sequence. Afusion protein comprising all or part of a polypeptide is one example ofa variant of the polypeptide.

A “derivative” of a polypeptide is a polypeptide (e.g., an antigenbinding protein, or an antibody) that has been chemically modified insome manner distinct from the insertion, deletion, and/or substitutionof amino acids, e.g., via conjugation to another chemical moiety. Anantigen binding protein that contains all or most of either the light-or heavy-chain variable domain of an antibody, but lacks most or all ofthe other variable domain of the antibody, is an example of a derivativeof the antibody.

The term “naturally occurring” as used throughout the specification inconnection with biological materials such as polypeptides, nucleicacids, host cells, and the like, refers to materials which are found innature.

An “antigen binding protein” as used herein means a protein thatspecifically binds a specified target antigen, such as IL-21 receptor orhuman IL-21-receptor.

An antigen binding protein, such as an antibody or antibody fragment,variant, or derivative, is said to “specifically bind” its targetantigen when it binds immunospecifically to its target antigen. In someembodiments, a specifically binding antigen binding protein has adissociation constant (K_(D)) of 1 to 10×10⁻⁸ M. The antibodyspecifically binds antigen with “high affinity” when the K_(D) is 1 to10×10⁻⁹ M, and with “very high affinity” when the K_(D) is 1 to 10×10⁻¹⁰M. In one embodiment, the antibody has a K_(D) of 1 to 10×10⁻⁹ M and anoff-rate of about 1×10⁻⁴/sec. In one embodiment, the off-rate is about1×10⁻⁵/sec. In other embodiments, the antibodies will bind to IL-21receptor, or human IL-21 receptor, with a K_(D) of between about 10⁻⁸ Mand 10⁻¹⁰ M, and in yet another embodiment it will bind with a K_(D) of1 to 2×10⁻¹⁰.

“Antigen binding region” means the portion of an antibody or otherantigen binding protein, or a fragment, derivative, or variant thereof,that specifically binds a specified antigen. An antigen binding regioncan include one or more “complementarity determining regions” (“CDRs”).Certain antigen binding regions also include one or more “framework”regions. Residues within the framework regions of some antibodies andother antigen binding proteins can contribute directly to the specificbinding of the antibody or antigen binding protein to its antigen, buttypically framework regions aid in maintaining a conformation of theCDRs that allows binding between the antigen binding region and theantigen.

In certain aspects, recombinant antigen binding proteins that bind 11-21receptor, or human IL-21 receptor, are provided. In this context, a“recombinant protein” is a protein made using recombinant techniques,e.g., through the expression of a recombinant nucleic acid. Methods andtechniques for the production of recombinant proteins are well known inthe art.

The term “antibody” refers to an intact antigen-binding immunoglobulinof any kind, or a fragment thereof that itself specifically binds to theantibody's target antigen, and includes, for example, chimeric,humanized, fully human, and bispecific antibodies. An “antibody” is atype of an antigen binding protein. In some embodiments, an intactantibody comprises two full-length heavy chains and two full-lengthlight chains. In other embodiments, an intact antibody includes fewerchains such as antibodies naturally occurring in camelids, which maycomprise only heavy chains. In other embodiments, a fragment orderivative of an antibody is made that lacks part or all of theantibody's light chains or light chain variable regions. In otherembodiments, a fragment or derivative of an antibody is made that lackssome or all of the antibody's heavy chains. Such derivatives orfragments typically will comprise one or more linker or other amino acidsequences to join the light chains or light chain fragments and/or allowthem to adopt a conformation that allows for binding of the fragment orderivative to its antigen.

The amino acid sequences of an antibody may be derived solely from asingle source, or may be “chimeric”; that is, different portions of theantibody may be derived from two different antibodies as describedfurther below. The antigen binding proteins, antibodies, or bindingfragments may be produced in hybridomas, by recombinant DNA techniques,or by enzymatic or chemical cleavage of intact antibodies. Unlessotherwise indicated, the term “antibody” includes, in addition toantibodies comprising two full-length heavy chains and two full-lengthlight chains, derivatives, variants, fragments, and mutations thereof.

The term “light chain” includes full-length light chain as well asfragments, derivatives, and variants thereof having a variable regionsequence that is sufficient, in combination, as needed, with a suitableheavy chain or heavy chain fragment, derivative, or variant, to conferspecific binding to an antigen. A full-length light chain includes avariable region domain, V_(L), and a constant region domain, C_(L).Examples of light chains include kappa light chains and lambda lightchains.

The term “heavy chain” includes a full-length heavy chain as well asfragments, derivatives, and variants thereof having a variable regionsequence that is sufficient, in combination, as needed, with a suitablelight chain or light chain fragment, derivative, or variant, to conferspecific binding to an antigen. A full-length heavy chain includes avariable region domain, V_(H), and three constant region domains,C_(H1), C_(H2), and C_(H3). Heavy chains may be of any isotype,including IgG (including IgG1, IgG2, IgG3 and IgG4 subtypes), IgA(including IgA1 and IgA2 subtypes), IgM and IgE, as well as derivativesand variants thereof.

The term “immunologically functional fragment” of an antibody orimmunoglobulin chain (heavy or light chain), as used herein, is anantigen binding protein comprising a portion (regardless of how thatportion is obtained or synthesized) of an antibody that lacks at leastsome of the amino acids present in a full-length chain but which iscapable of specifically binding to an antigen. Such fragments arebiologically active in that they bind specifically to the targetantigen. In some embodiment, such a fragment will retain at least oneCDR present in the full-length light or heavy chain, and in someembodiments will comprise a single heavy chain and/or light chain orportion thereof. These biologically active fragments may be produced by,for example, recombinant DNA techniques or by enzymatic or chemicalcleavage of antigen binding proteins, including of intact antibodies.Immunologically functional immunoglobulin fragments include, but are notlimited to, Fab, Fab′, F(ab′)₂, Fv, domain antibodies and single-chainantibodies, and may be derived from any mammalian source, including butnot limited to human, mouse, rat, camelid or rabbit. It is contemplatedfurther that a functional portion of the antigen binding proteinsdisclosed herein, for example, one or more CDRs, could be covalentlybound to a second protein or to a small molecule to create a therapeuticagent directed to a particular target in the body, possessingbifunctional therapeutic properties, or having a prolonged serumhalf-life.

“Single-chain antibodies” are Fv molecules in which the heavy and lightchain variable regions have been connected by a flexible linker to forma single polypeptide chain, which forms an antigen-binding region.Single chain antibodies are discussed in detail in International PatentApplication Publication No. WO 88/01649 and U.S. Pat. No. 4,946,778 andNo. 5,260,203, the disclosures of which are incorporated by reference.

A “domain antibody” is an immunologically functional immunoglobulinfragment containing only the variable region of a heavy chain or thevariable region of a light chain. In some instances, two or more V_(H)regions are covalently joined with a peptide linker to create a bivalentdomain antibody. The two V_(H) regions of a bivalent domain antibody maytarget the same or different antigens.

A “bivalent antigen binding protein” or “bivalent antibody” comprisestwo antigen binding sites.

In some embodiments, the two binding sites have the same antigenspecificities. In other embodiments, the bivalent antigen bindingproteins and bivalent antibodies are bispecific.

A multispecific antigen binding protein” or “multispecific antibody” isone that specifically binds more than one antigen or epitope.

A “bispecific,” “dual-specific” or “bifunctional” antigen bindingprotein or antibody is a hybrid antigen binding protein or antibody,respectively, having two antigen binding sites that each specificallybinds to a different epitope. The two epitopes can be present on thesame molecule (e.g., on the IL-21 receptor protein) or on differentmolecules (e.g., on the IL-21 receptor protein and on IL-21, or on IL-21receptor and on the common gamma chain). Bispecific antigen bindingproteins and antibodies are a species of multispecific antigen bindingprotein or multispecific antibody and may be produced by a variety ofmethods including, but not limited to, fusion of hybridomas or linkingof Fab′ fragments. See, e.g., Songsivilai and Lachmann, 1990, Clin. Exp.Immunol 79:315-321; Kostelny et al., 1992, J. Immunol. 148:1547-1553.

The terms “inhibitory antigen binding protein,” “inhibitory antibody,”“antagonistic antigen binding protein,” “antagonistic antibody,”“neutralizing antigen binding protein” and “neutralizing antibody”refers to an antigen binding protein or antibody, respectively, thatspecifically binds to its target and thereby reduces or prevents abiological activity of the target, such as, for example, its ability tobind with a ligand, receptor, binding partner, regulatory molecule, orsubstrate, catalyze a reaction, send or propagate a signal, orphosphorylate or de-phosphorylate itself or another protein.

The term “compete” when used in the context of antigen binding proteins(e.g., neutralizing antigen binding proteins or neutralizing antibodies)that bind to the same target means competition between antigen bindingproteins is determined by an assay in which the antigen binding protein(e.g., antibody or immunologically functional fragment thereof) undertest prevents, reduces or inhibits specific binding of a referenceantigen binding protein (e.g., a ligand, or a reference antibody) to acommon antigen (e.g., IL-21 receptor or a fragment thereof). Numeroustypes of competitive binding assays can be used, for example: solidphase direct or indirect radioimmunoassay (RIA), solid phase direct orindirect enzyme immunoassay (EIA), sandwich competition assay (see,e.g., Stahli et al., 1983, Methods in Enzymology 9:242-253); solid phasedirect biotin-avidin EIA (see, e.g., Kirkland et al., 1986, J. Immunol.137:3614-3619) solid phase direct labeled assay, solid phase directlabeled sandwich assay (see, e.g., Harlow and Lane, 1988, Antibodies, ALaboratory Manual, Cold Spring Harbor Press); solid phase direct labelRIA using 1-125 label (see, e.g., Morel et al., 1988, Molec. Immunol.25:7-15); solid phase direct biotin-avidin EIA (see, e.g., Cheung, etal., 1990, Virology 176:546-552); and direct labeled RIA (Moldenhauer etal., 1990, Scand. J. Immunol. 32:77-82). Typically, such an assayinvolves the use of purified antigen bound to a solid surface or cellsbearing either of these, an unlabelled test antigen binding protein anda labeled reference antigen binding protein. Competitive inhibition ismeasured by determining the amount of label bound to the solid surfaceor cells in the presence of the test antigen binding protein. Usuallythe test antigen binding protein is present in excess. Antigen bindingproteins identified by competition assay (competing antigen bindingproteins) include antigen binding proteins binding to the same epitopeas the reference antigen binding proteins, an epitope that overlaps theepitope as the reference antigen binding proteins, and epitopes that donot overlap but that allow for steric hindrance to occur between thetest and reference antigen binding proteins. A specific method fordetermining competitive binding is provided in the examples herein.Usually, when a competing antigen binding protein is present in excess,it will inhibit specific binding of a reference antigen binding proteinto a common antigen by at least 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%,60%, 65%, 70% or 75%. In some instance, binding is inhibited by at least80%, 85%, 90%, 95%, or 97% or more.

The term “antigen” refers to a molecule or a portion of a moleculecapable of being bound by a selective binding agent, such as an antigenbinding protein (including, e.g., an antibody or immunologicalfunctional fragment thereof), and additionally capable of being used inan animal to produce antibodies capable of binding to that antigen. Anantigen may possess one or more epitopes that are capable of interactingwith different antigen binding proteins, e.g., antibodies.

The term “epitope” is the portion of a molecule that is bound by anantigen binding protein (for example, an antibody). The term includesany determinant capable of specifically binding to an antigen bindingprotein, such as an antibody or to a T-cell receptor. An epitope can becontiguous or non-contiguous (e.g., in a polypeptide, amino acidresidues that are not contiguous to one another in the polypeptidesequence but that within in context of the molecule are bound by theantigen binding protein). In certain embodiments, epitopes may bemimetic in that they comprise a three dimensional structure that issimilar to an epitope used to generate the antigen binding protein, yetcomprise none or only some of the amino acid residues found in thatepitope used to generate the antigen binding protein. Most often,epitopes reside on proteins, but in some instances may reside on otherkinds of molecules, such as nucleic acids. Epitope determinants mayinclude chemically active surface groupings of molecules such as aminoacids, sugar side chains, phosphoryl or sulfonyl groups, and may havespecific three dimensional structural characteristics, and/or specificcharge characteristics. Generally, antibodies specific for a particulartarget antigen will preferentially recognize an epitope on the targetantigen in a complex mixture of proteins and/or macromolecules.

The term “identity” refers to a relationship between the sequences oftwo or more polypeptide molecules or two or more nucleic acid molecules,as determined by aligning and comparing the sequences. “Percentidentity” means the percent of identical residues between the aminoacids or nucleotides in the compared molecules and is calculated basedon the size of the smallest of the molecules being compared. For thesecalculations, gaps in alignments (if any) must be addressed by aparticular mathematical model or computer program (i.e., an“algorithm”). Methods that can be used to calculate the identity of thealigned nucleic acids or polypeptides include those described inComputational Molecular Biology, (Lesk, A. M., ed.), 1988, New York:Oxford University Press; Biocomputing Informatics and Genome Projects,(Smith, D. W., ed.), 1993, New York: Academic Press; Computer Analysisof Sequence Data, Part I, (Griffin, A. M., and Griffin, H. G., eds.),1994, New Jersey: Humana Press; von Heinje, G., 1987, Sequence Analysisin Molecular Biology, New York: Academic Press; Sequence AnalysisPrimer, (Gribskov, M. and Devereux, J., eds.), 1991, New York: M.Stockton Press; and Carillo et al., 1988, SIAM J. Applied Math. 48:1073.

In calculating percent identity, the sequences being compared arealigned in a way that gives the largest match between the sequences. Thecomputer program used to determine percent identity is the GCG programpackage, which includes GAP (Devereux et al., 1984, Nucl. Acid Res.12:387; Genetics Computer Group, University of Wisconsin, Madison,Wis.). The computer algorithm GAP is used to align the two polypeptidesor polynucleotides for which the percent sequence identity is to bedetermined. The sequences are aligned for optimal matching of theirrespective amino acid or nucleotide (the “matched span”, as determinedby the algorithm). A gap opening penalty (which is calculated as 3× theaverage diagonal, wherein the “average diagonal” is the average of thediagonal of the comparison matrix being used; the “diagonal” is thescore or number assigned to each perfect amino acid match by theparticular comparison matrix) and a gap extension penalty (which isusually 1/10 times the gap opening penalty), as well as a comparisonmatrix such as PAM 250 or BLOSUM 62 are used in conjunction with thealgorithm. In certain embodiments, a standard comparison matrix (see,Dayhoff et al., 1978, Atlas of Protein Sequence and Structure 5:345-352for the PAM 250 comparison matrix; Henikoff et al., 1992, Proc. Natl.Acad. Sci. USA. 89:10915-10919 for the BLOSUM 62 comparison matrix) isalso used by the algorithm.

Parameters for determining percent identity for polypeptides ornucleotide sequences using the GAP program are the following:

Algorithm: Needleman et al., 1970, J. Mol. Biol. 48:443-453;

Comparison matrix: BLOSUM 62 from Henikoff et al., 1992, supra;

Gap Penalty: 12 (but with no penalty for end gaps)

Gap Length Penalty: 4

Threshold of Similarity: 0

Certain alignment schemes for aligning two amino acid sequences mayresult in matching of only a short region of the two sequences, and thissmall aligned region may have very high sequence identity even thoughthere is no significant relationship between the two full-lengthsequences. Accordingly, the selected alignment method (GAP program) canbe adjusted if so desired to result in an alignment that spans at least50 contiguous amino acids of the target polypeptide.

As used herein, “substantially pure” means that the described species ofmolecule is the predominant species present, that is, on a molar basisit is more abundant than any other individual species in the samemixture. In certain embodiments, a substantially pure molecule is acomposition wherein the object species comprises at least 50% (on amolar basis) of all macromolecular species present. In otherembodiments, a substantially pure composition will comprise at least80%, 85%, 90%, 95%, or 99% of all macromolecular species present in thecomposition. In other embodiments, the object species is purified toessential homogeneity wherein contaminating species cannot be detectedin the composition by conventional detection methods and thus thecomposition consists of a single detectable macromolecular species.

The term “treating” refers to any indicia of success in the prevention,prophylaxis, treatment or amelioration of an injury, pathology, diseaseor condition, including any objective or subjective parameter such asabatement; remission; diminishing of symptoms or making the injury,pathology or condition more tolerable to the patient; slowing in therate of degeneration or decline; making the final point of degenerationless debilitating; improving a patient's physical or mental well-being.The treatment or amelioration of symptoms can be based on objective orsubjective parameters; including the results of a physical examination,neuropsychiatric exams, and/or a psychiatric evaluation. For example,certain methods presented herein successfully treat inflammatoryconditions by decreasing the incidence of inflammation, causingremission of inflammation and/or ameliorating a symptom associated withinflammation.

An “effective amount” of a therapeutic treatment is generally an amountsufficient to reduce the severity and/or frequency of symptoms,eliminate the symptoms and/or underlying cause, prevent the occurrenceof symptoms and/or their underlying cause, and/or improve or remediatethe damage that results from or is associated with symptoms or theirunderlying cause. In some embodiments, the effective amount is atherapeutically effective amount or a prophylactically effective amount.A “therapeutically effective amount” is an amount sufficient to remedy adisease state (e.g. inflammation) or symptoms, particularly a state orsymptoms associated with the disease state, or otherwise prevent,hinder, retard or reverse the progression of the disease state or anyother undesirable symptom associated with the disease in any waywhatsoever. A “prophylactically effective amount” is an amount of apharmaceutical composition that, when administered to a subject, willhave the intended prophylactic effect, e.g., preventing or delaying theonset (or reoccurrence) of inflammation, or reducing the likelihood ofthe onset (or reoccurrence) of inflammation or inflammation symptoms.The full therapeutic or prophylactic effect does not necessarily occurby administration of one dose, and may occur only after administrationof a series of doses. Thus, a therapeutically or prophylacticallyeffective amount may be administered in one or more administrations.

“Amino acid” includes its normal meaning in the art. The twentynaturally-occurring amino acids and their abbreviations followconventional usage. See, Immunology—A Synthesis, 2nd Edition, (E. S.Golub and D. R. Green, eds.), Sinauer Associates: Sunderland, Mass.(1991), incorporated herein by reference for any purpose. Stereoisomers(e.g., D-amino acids) of the twenty conventional amino acids, unnaturalamino acids such as [alpha]-, [alpha]-disubstituted amino acids, N-alkylamino acids, and other unconventional amino acids may also be suitablecomponents for polypeptides and are included in the phrase “amino acid.”Examples of unconventional amino acids include: 4-hydroxyproline,[gamma]-carboxyglutamate, [epsilon]-N,N,N-trimethyllysine,[epsilon]-N-acetyllysine, O-phosphoserine, N-acetylserine,N-formylmethionine, 3-methylhistidine, 5-hydroxylysine,[sigma]-N-methylarginine, and other similar amino acids and imino acids(e.g., 4-hydroxyproline). In the polypeptide notation used herein, theleft-hand direction is the amino terminal direction and the right-handdirection is the carboxyl-terminal direction, in accordance withstandard usage and convention.

The term “IL-21 receptor mediated disease” includes, but is not limitedto, inflammatory, infectious, and autoimmune diseases. An “autoimmunedisease” as used herein refers to disease states and conditions whereina patient's immune response is directed toward the patient's ownconstituents. For example, IL-21 receptor mediated diseases include, butare not limited to, Acquired Immune Deficiency Syndrome (AIDS),rheumatoid arthritis including juvenile rheumatoid arthritis,inflammatory bowel diseases including ulcerative colitis and Crohn'sdisease, multiple sclerosis, Addison's disease, diabetes (type I),diabetes (type 2), insulin resistance, metabolic syndrome, heartdisease, coronary artery disease, epididymitis, glomerulonephritis,Graves' disease, Guillain-Barre syndrome, Hashimoto's disease, hemolyticanemia, systemic lupus erythematosus (SLE), lupus nephritis, myastheniagravis, pemphigus, psoriasis, psoriatic arthritis, atherosclerosis,erythropoietin resistance, graft versus host disease, transplantrejection, autoimmune hepatitis-induced hepatic injury, biliarycirrhosis, alcohol-induced liver injury including alcoholic cirrhosis,rheumatic fever, sarcoidosis, scleroderma, Sjogren's syndrome,spondyloarthropathies including ankylosing spondylitis, thyroiditis,vasculitis, atherosclerosis, coronary artery disease, and heart disease.The term “IL-21 receptor mediated disease” also encompasses any medicalcondition associated with increased levels of IL-21 or IL-21 receptor orincreased sensitivity to IL-21.

Antigen Binding Proteins

In one aspect, the present invention provides antigen binding proteins(e.g., antibodies, antibody fragments, antibody derivatives, antibodymuteins, and antibody variants), that bind to IL-21 receptor, e.g.,human IL-21 receptor.

Antigen binding proteins in accordance with the present inventioninclude antigen binding proteins that inhibit a biological activity ofIL-21 receptor. Examples of such biological activities include binding asignaling molecule (e.g., IL-21), and transducing a signal in responseto binding a signaling molecule.

Different antigen binding proteins may bind to different domains orepitopes of IL-21 receptor or act by different mechanisms of action.Examples include but are not limited to antigen binding proteins thatinterfere with binding of IL-21 to IL-21 receptor or that inhibit signaltransduction. The site of action may be, for example, intracellular(e.g., by interfering with an intracellular signaling cascade) orextracellular. An antigen binding protein need not completely inhibit anIL-21 induced activity to find use in the present invention; rather,antigen binding proteins that reduce a particular activity of IL-21 arecontemplated for use as well. (Discussions herein of particularmechanisms of action for IL-21 receptor-binding antigen binding proteinsin treating particular diseases are illustrative only, and the methodspresented herein are not bound thereby.)

In another aspect, the present invention provides IL-21 receptor antigenbinding proteins that comprise a light chain variable region and/or aheavy chain variable region selected from the sequences provided herein,or that comprise one or more CDR sequences selected from the sequencesprovided herein. Examples of antigen binding proteins of the presentinvention include antigen binding proteins, antibodies, and antibodyderivatives and fragments comprising all or part of the sequences ofantibodies 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, and37G3 as disclosed in FIGS. 2 through 13 or in the Examples. Specificfragments of these antibodies that are found in various embodiments ofthe invention include their signal sequences, variable domains, CDRs,framework regions, and constant regions. In one such embodiment, theantigen binding protein comprises the heavy chain variable domain ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3.In another such embodiment, the antigen binding protein comprises thelight chain variable domain of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3. In another such embodiment, the antigenbinding protein comprises the light chain variable domain and the heavychain variable domain of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2,31E7, 34H7, 30G3, or 37G3. In another such embodiment, the antigenbinding protein comprises the heavy chain CDR sequences of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3. Inanother such embodiment, the antigen binding protein comprises the lightchain CDR sequences of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2,31E7, 34H7, 30G3, or 37G3. In another such embodiment, the antigenbinding protein comprises the heavy chain CDR sequences and the lightchain CDR sequences of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2,31E7, 34H7, 30G3, or 37G3. In some such embodiments, the antigen bindingprotein is an antibody or an antigen-binding fragment of an antibody.

In one embodiment, the present invention provides an IL-21 receptorantigen binding protein comprising a heavy chain variable domainselected from the 31C5 group, the 29G2 group, the 31E7 group, the 34H7group, the 30G3 group, or the 37G3 group, of FIG. 12. In anotherembodiment, the present invention provides an IL-21 receptor antigenbinding protein comprising a light chain variable domain selected fromthe 10C2 group, the 8B9 group, the 29G8 group, the 31C5 group, the 29G2group, the 31E7 group, 34H7 group, the 30G3 group, or the 37G3 group, ofFIG. 13. In another embodiment, the present invention provides an IL-21receptor antigen binding protein comprising a heavy chain variabledomain selected from the 31C5 group, the 29G2 group, the 31E7 group, the34H7 group, the 30G3 group, or the 37G3 group, of FIG. 12, and a lightchain variable domain selected from the corresponding group of FIG. 13.In another embodiment, the present invention provides an IL-21 receptorantigen binding protein comprising a light chain variable domainselected from the 10C2 group, the 8B9 group, the 29G8 group, the 31C5group, the 29G2 group, the 31E7 group, 34H7 group, the 30G3 group, orthe 37G3 group, of FIG. 13, and a heavy chain variable domain selectedfrom the corresponding group of FIG. 12. In another embodiment, thepresent invention provides an IL-21 receptor antigen binding proteincomprising heavy chain CDR 1, 2, and 3 sequences selected from one ormore antibodies within the 31C5 group, the 29G2 group, the 31E7 group,the 34H7 group, the 30G3 group, or the 37G3 group, of FIG. 12, and lightchain CDR 1, 2, and 3 sequences selected from one or more antibodieswithin the corresponding group of FIG. 13.

In another embodiment, the present invention provides an IL-21 receptorantigen binding protein comprising a light chain variable domaincomprising a sequence of amino acids that differs from the sequence of alight chain variable domain disclosed in FIG. 4, 9, 11, or 13, or in theExamples, only at 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1residues, wherein each such sequence difference is independently eithera deletion, insertion, or substitution of one amino acid residue. Inanother embodiment, the light-chain variable domain comprises a sequenceof amino acids that is at least 70%, 75%, 80%, 85%, 90%, 95%, 97%, or99% identical to the sequence of a light chain variable domain selectedfrom the light chain variable domain sequences disclosed in FIG. 4, 9,11, or 13, or in the Examples. In another embodiment, the light chainvariable domain comprises a sequence of amino acids that is encoded by anucleotide sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, 97%,or 99% identical to a nucleotide sequence disclosed in FIG. 5A or 5B. Inanother embodiment, the light chain variable domain comprises a sequenceof amino acids that is encoded by a polynucleotide that hybridizes undermoderately stringent conditions to the complement of a polynucleotidedisclosed in FIG. 5A or 5B. In another embodiment, the light chainvariable domain comprises a sequence of amino acids that is encoded by apolynucleotide that hybridizes under moderately stringent conditions tothe complement of a polynucleotide disclosed in FIG. 5A or 5B. Inanother embodiment, the light chain variable domain comprises a sequenceof amino acids that is encoded by a polynucleotide that hybridizes undermoderately stringent conditions to a complement of a light chainpolynucleotide disclosed in FIG. 5A or 5B.

In another embodiment, the present invention provides an IL-21 receptorantigen binding protein comprising a heavy chain variable domaincomprising a sequence of amino acids that differs from the sequence of aheavy chain variable domain selected disclosed in FIG. 2, 8, 10, or 12,or in the Examples, only at 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3,2, or 1 residue(s), wherein each such sequence difference isindependently either a deletion, insertion, or substitution of one aminoacid residue. In another embodiment, the heavy chain variable domaincomprises a sequence of amino acids that is at least 70%, 75%, 80%, 85%,90%, 95%, 97%, or 99% identical to the sequence of a heavy chainvariable domain sequence disclosed in FIG. 2, 8, 10, or 12, or in theExamples. In another embodiment, the heavy chain variable domaincomprises a sequence of amino acids that is encoded by a nucleotidesequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, 97%, or 99%identical to a nucleotide sequence disclosed in FIG. 3A or 3B. Inanother embodiment, the heavy chain variable domain comprises a sequenceof amino acids that is encoded by a polynucleotide that hybridizes undermoderately stringent conditions to the complement of a polynucleotidedisclosed in FIG. 3A or 3B. In another embodiment, the heavy chainvariable domain comprises a sequence of amino acids that is encoded by apolynucleotide that hybridizes under moderately stringent conditions tothe complement of a polynucleotide disclosed in FIG. 3A or 3B. Inanother embodiment, the heavy chain variable domain comprises a sequenceof amino acids that is encoded by a polynucleotide that hybridizes undermoderately stringent conditions to a complement of a heavy chainpolynucleotide disclosed in FIG. 3A or 3B.

Particular embodiments of antigen binding proteins of the presentinvention comprise one or more amino acid sequences that are identicalto the amino acid sequences of one or more of the CDRs and/or FRsdisclosed in FIG. 2, 4, 6, 8, 9, 10, 11, 12 or 13, or in the Examples.In one embodiment, the antigen binding protein comprises a light chainCDR1 sequence disclosed in FIG. 4, 6, or 13, or in the Examples. Inanother embodiment, the antigen binding protein comprises a light chainCDR2 sequence disclosed in FIG. 4, 6, or 13, or in the Examples. Inanother embodiment, the antigen binding protein comprises a light chainCDR3 sequence disclosed in FIG. 4, 6, or 13, or in the Examples. Inanother embodiment, the antigen binding protein comprises a heavy chainCDR1 sequence disclosed in FIG. 2, 6, or 12, or in the Examples. Inanother embodiment, the antigen binding protein comprises a heavy chainCDR2 sequence disclosed in FIG. 2, 6, or 12, or in the Examples. Inanother embodiment, the antigen binding protein comprises a heavy chainCDR3 sequence disclosed in FIG. 2, 6, or 12, or in the Examples. Inanother embodiment, the antigen binding protein comprises a light chainFR1 sequence disclosed herein. In another embodiment, the antigenbinding protein comprises a light chain FR2 sequence disclosed herein.In another embodiment, the antigen binding protein comprises a lightchain FR3 sequence disclosed herein. In another embodiment, the antigenbinding protein comprises a light chain FR4 sequence disclosed herein.In another embodiment, the antigen binding protein comprises a heavychain FR1 sequence disclosed herein. In another embodiment, the antigenbinding protein comprises a heavy chain FR2 sequence disclosed herein.In another embodiment, the antigen binding protein comprises a heavychain FR3 sequence disclosed herein. In another embodiment, the antigenbinding protein comprises a heavy chain FR4 sequence disclosed herein.

In one embodiment, the present invention provides an antigen bindingprotein that comprises one or more CDR sequences that each differs froma CDR sequence disclosed in FIG. 2, 6, 12, or 13, or in the Examples, byno more than 5, 4, 3, 2, or 1 amino acid residues.

In another embodiment, the present invention provides antibodies thatcross-compete with antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, and/or 37G3 for binding to the extracellular domain humanIL-21 receptor, wherein two antibodies “cross-compete” if each antibodyreduces the binding of the other by at least 80% in the assay describedin Example 4.

The nucleotide sequences or amino acid sequences disclosed herein can bealtered, for example, by random mutagenesis or by site-directedmutagenesis (e.g., oligonucleotide-directed site-specific mutagenesis)to create an altered polynucleotide comprising one or more particularnucleotide substitutions, deletions, or insertions as compared to thenon-mutated polynucleotide. Examples of techniques for making suchalterations are described in Walder et al., 1986, Gene 42:133; Bauer etal. 1985, Gene 37:73; Craik, BioTechniques, January 1985, 12-19; Smithet al., 1981, Genetic Engineering: Principles and Methods, Plenum Press;and U.S. Pat. Nos. 4,518,584 and 4,737,462. These and other methods canbe used to make, for example, derivatives of anti-IL-21 receptorantibodies that have a desired property, for example, increasedaffinity, avidity, or specificity for IL-21 receptor, increased activityor stability in vivo or in vitro, or reduced in vivo side-effects ascompared to the underivatized antibody.

Other derivatives of anti-IL-21 receptor antibodies within the scope ofthis invention include covalent or aggregative conjugates of anti-IL-21receptor antibodies, or fragments thereof, with other proteins orpolypeptides, such as by expression of recombinant fusion proteinscomprising heterologous polypeptides fused to the N-terminus orC-terminus of an anti-IL-21 receptor antibody polypeptide. For example,the conjugated peptide may be a heterologous signal (or leader)polypeptide, e.g., the yeast alpha-factor leader, or a peptide such asan epitope tag. Antigen binding protein-containing fusion proteins cancomprise peptides added to facilitate purification or identification ofantigen binding protein (e.g., poly-His). An antigen binding proteinalso can be linked to the FLAG peptide Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys(DYKDDDDK) (SEQ ID NO: 1) as described in Hopp et al., Bio/Technology6:1204, 1988, and U.S. Pat. No. 5,011,912. The FLAG peptide is highlyantigenic and provides an epitope reversibly bound by a specificmonoclonal antibody (mAb), enabling rapid assay and facile purificationof expressed recombinant protein. Reagents useful for preparing fusionproteins in which the FLAG peptide is fused to a given polypeptide arecommercially available (Sigma, St. Louis, Mo.).

Oligomers that contain one or more antigen binding proteins may beemployed as IL-21 receptor antagonists. Oligomers may be in the form ofcovalently-linked or non-covalently-linked dimers, trimers, or higheroligomers. Oligomers comprising two or more antigen binding protein arecontemplated for use, with one example being a homodimer. Otheroligomers include heterodimers, homotrimers, heterotrimers,homotetramers, heterotetramers, etc.

One embodiment is directed to oligomers comprising multiple antigenbinding proteins joined via covalent or non-covalent interactionsbetween peptide moieties fused to theantigen binding proteins. Suchpeptides may be peptide linkers (spacers), or peptides that have theproperty of promoting oligomerization. Leucine zippers and certainpolypeptides derived from antibodies are among the peptides that canpromote oligomerization of antigen binding proteins attached thereto, asdescribed in more detail below.

In particular embodiments, the oligomers comprise from two to fourantigen binding proteins. The antigen binding proteins of the oligomermay be in any form, such as any of the forms described above, e.g.,variants or fragments. Preferably, the oligomers comprise antigenbinding proteins that have IL-21 receptor binding activity.

In one embodiment, an oligomer is prepared using polypeptides derivedfrom immunoglobulins. Preparation of fusion proteins comprising certainheterologous polypeptides fused to various portions of antibody-derivedpolypeptides (including the Fc domain) has been described, e.g., byAshkenazi et al., 1991, PNAS USA 88:10535; Byrn et al., 1990, Nature344:677; and Hollenbaugh et al., 1992 “Construction of ImmunoglobulinFusion Proteins”, in Current Protocols in Immunology, Suppl. 4, pages10.19.1-10.19.11.

One embodiment of the present invention is directed to a dimercomprising two fusion proteins created by fusing an IL-21 receptorbinding fragment of an anti-IL-21 receptor antibody to the Fc region ofan antibody. The dimer can be made by, for example, inserting a genefusion encoding the fusion protein into an appropriate expressionvector, expressing the gene fusion in host cells transformed with therecombinant expression vector, and allowing the expressed fusion proteinto assemble much like antibody molecules, whereupon interchain disulfidebonds form between the Fc moieties to yield the dimer

The term “Fc polypeptide” as used herein includes native and muteinforms of polypeptides derived from the Fc region of an antibody.Truncated forms of such polypeptides containing the hinge region thatpromotes dimerization also are included. Fusion proteins comprising Fcmoieties (and oligomers formed therefrom) offer the advantage of facilepurification by affinity chromatography over Protein A or Protein Gcolumns.

One suitable Fc polypeptide, described in PCT application WO 93/10151(hereby incorporated by reference), is a single chain polypeptideextending from the N-terminal hinge region to the native C-terminus ofthe Fc region of a human IgG1 antibody. Another useful Fc polypeptide isthe Fc mutein described in U.S. Pat. No. 5,457,035 and in Baum et al.,1994, EMBO J. 13:3992-4001. The amino acid sequence of this mutein isidentical to that of the native Fc sequence presented in WO 93/10151,except that amino acid 19 has been changed from Leu to Ala, amino acid20 has been changed from Leu to Glu, and amino acid 22 has been changedfrom Gly to Ala. The mutein exhibits reduced affinity for Fc receptors.

In other embodiments, the variable portion of the heavy and/or lightchains of an anti-IL-21 receptor antibody may be substituted for thevariable portion of an antibody heavy and/or light chain.

Alternatively, the oligomer is a fusion protein comprising multipleantigen binding proteins, with or without peptide linkers (spacerpeptides). Among the suitable peptide linkers are those described inU.S. Pat. Nos. 4,751,180 and 4,935,233.

Another method for preparing oligomeric antigen binding proteinsinvolves use of a leucine zipper. Leucine zipper domains are peptidesthat promote oligomerization of the proteins in which they are found.Leucine zippers were originally identified in several DNA-bindingproteins (Landschulz et al., 1988, Science 240:1759), and have sincebeen found in a variety of different proteins. Among the known leucinezippers are naturally occurring peptides and derivatives thereof thatdimerize or trimerize. Examples of leucine zipper domains suitable forproducing soluble oligomeric proteins are described in PCT applicationWO 94/10308, and the leucine zipper derived from lung surfactant proteinD (SPD) described in Hoppe et al., 1994, FEBS Letters 344:191, herebyincorporated by reference. The use of a modified leucine zipper thatallows for stable trimerization of a heterologous protein fused theretois described in Fanslow et al., 1994, Semin. Immunol. 6:267-78. In oneapproach, recombinant fusion proteins comprising an anti-IL-21 receptorantibody fragment or derivative fused to a leucine zipper peptide areexpressed in suitable host cells, and the soluble oligomeric anti-IL-21receptor antibody fragments or derivatives that form are recovered fromthe culture supernatant.

In another aspect, the present invention provides an antigen bindingprotein that binds to the ligand binding domain of human IL-21 receptor.Antigen binding proteins that bind to the ligand binding domain can bemade using any technique known in the art. For example, such antigenbinding proteins can be isolated using the full-length IL-21 receptorpolypeptide (e.g., in a membrane-bound preparation), a solubleextracellular domain fragment of IL-21 receptor, or a smaller fragmentof the IL-21 receptor extracellular domain comprising or consisting ofthe ligand binding domain. Antigen binding proteins so isolated can bescreened to determine their binding specificity using any method knownin the art. Examples of suitable assays are assays that test the antigenbinding proteins for the ability to inhibit binding of IL-21 to cellsexpressing IL-21 receptor, or that test antigen binding proteins for theability to reduce a biological or cellular response that results fromthe binding of IL-21 to cell surface IL-21 receptor receptors.

In another aspect, the present invention provides an antigen bindingprotein that binds to the same epitope as a reference antibody disclosedherein, for example, 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7,30G3, or 37G3, as disclosed in FIGS. 2 through 13 or in the Examples. Inone embodiment, the antigen binding protein competes for binding tohuman IL-21 receptor with the reference antibody. In another embodiment,the antigen binding protein and the reference antibody cross-compete forbinding to human IL-21 receptor. In another embodiment, the epitope ofthe reference antibody and of the antigen binding protein is determinedby solving the X-ray crystal structure of the antibody or antigenbinding protein bound to human IL-21 receptor, for example, to a solublefragment of human IL-21 receptor. In one such embodiment, the epitope isdefined as those residues on the surface of human IL-21 receptor thatshow at least a 10% reduction in solvent accessibility when thereference antibody or the antigen binding protein is bound to it ascompared to when it is bound to neither. In one embodiment, the epitopesubstantially overlaps the IL-21 binding domain of human IL-21 receptor.

In another aspect, the present invention provides an antigen bindingprotein that demonstrates species selectivity. In one embodiment, theantigen binding protein binds to one or more mammalian IL-21 receptors,for example, to human IL-21 receptor and to one or more of mouse, rat,guinea pig, hamster, gerbil, cat, rabbit, dog, goat, sheep, cow, horse,camel, and non-human primate IL-21 receptor. In another embodiment, theantigen binding protein binds to one or more primate IL-21 receptors,for example, to human IL-21 receptor and to one or more of cynomologous,marmoset, rhesus, and chimpanzee IL-21 receptors. In another embodiment,the antigen binding protein binds specifically to human, cynomologous,marmoset, rhesus, or chimpanzee IL-21 receptor. In another embodiment,the antigen binding protein does not bind to one or more of mouse, rat,guinea pig, hamster, gerbil, cat, rabbit, dog, goat, sheep, cow, horse,camel, and non-human primate IL-21 receptor. In another embodiment, theantigen binding protein does not bind to a New World monkey species suchas a marmoset. In another embodiment, the antigen binding protein doesnot exhibit specific binding to any naturally occurring protein otherthan IL-21 receptor. In another embodiment, the antigen binding proteindoes not exhibit specific binding to any naturally occurring proteinother than mammalian IL-21 receptor. In another embodiment, the antigenbinding protein does not exhibit specific binding to any naturallyoccurring protein other than primate IL-21 receptor. In anotherembodiment, the antigen binding protein does not exhibit specificbinding to any naturally occurring protein other than human IL-21receptor. In another embodiment, the antigen binding proteinspecifically binds to mouse, rat, cynomolgus monkey, and human IL-21receptor. In another embodiment, the antigen binding proteinspecifically binds to mouse, rat, cynomolgus monkey, and human IL-21receptor with a similar binding affinity. In another embodiment, theantigen binding protein blocks binding of human IL-21 with mouse, rat,cynomolgus monkey, and human IL-21 receptor. In another embodiment, theantigen binding protein blocks binding of human IL-21 with mouse, rat,cynomolgus monkey, and human IL-21 receptor with similar K.

One may determine the selectivity of an antigen binding protein for anIL-21 receptor using methods well known in the art and following theteachings of the specification. For example, one may determine theselectivity using Western blot, FACS, ELISA or RIA.

Antigen-binding fragments of antigen binding proteins of the inventionmay be produced by conventional techniques. Examples of such fragmentsinclude, but are not limited to, Fab and F(ab′)2 fragments. Antibodyfragments and derivatives produced by genetic engineering techniquesalso are contemplated.

Additional embodiments include chimeric antibodies, e.g., humanizedversions of non-human (e.g., murine) monoclonal antibodies. Suchhumanized antibodies may be prepared by known techniques, and offer theadvantage of reduced immunogenicity when the antibodies are administeredto humans. In one embodiment, a humanized monoclonal antibody comprisesthe variable domain of a murine antibody (or all or part of the antigenbinding site thereof) and a constant domain derived from a humanantibody. Alternatively, a humanized antibody fragment may comprise theantigen binding site of a murine monoclonal antibody and a variabledomain fragment (lacking the antigen-binding site) derived from a humanantibody. Procedures for the production of chimeric and furtherengineered monoclonal antibodies include those described in Riechmann etal., 1988, Nature 332:323, Liu et al., 1987, Proc. Nat. Acad. Sci. USA84:3439, Larrick et al., 1989, Bio/Technology 7:934, and Winter et al.,1993, TIPS 14:139. In one embodiment, the chimeric antibody is a CDRgrafted antibody. Techniques for humanizing antibodies are discussed in,e.g., U.S. patent application Ser. No. 10/194,975 (published Feb. 27,2003), U.S. Pat. Nos. 5,869,619, 5,225,539, 5,821,337, 5,859,205, Padlanet al., 1995, FASEB J. 9:133-39, and Tamura et al., 2000, J. Immunol.164:1432-41.

Procedures have been developed for generating human or partially humanantibodies in non-human animals. For example, mice in which one or moreendogenous immunoglobulin genes have been inactivated by various meanshave been prepared. Human immunoglobulin genes have been introduced intothe mice to replace the inactivated mouse genes. Antibodies produced inthe animal incorporate human immunoglobulin polypeptide chains encodedby the human genetic material introduced into the animal. In oneembodiment, a non-human animal, such as a transgenic mouse, is immunizedwith an IL-21 receptor polypeptide, such that antibodies directedagainst the IL-21 receptor polypeptide are generated in the animal. Oneexample of a suitable immunogen is a soluble human IL-21 receptor, suchas a polypeptide comprising its extracellular domain or otherimmunogenic fragment. Examples of techniques for production and use oftransgenic animals for the production of human or partially humanantibodies are described in U.S. Pat. Nos. 5,814,318, 5,569,825, and5,545,806, Davis et al., 2003, Production of human antibodies fromtransgenic mice in Lo, ed. Antibody Engineering: Methods and Protocols,Humana Press, NJ: 191-200, Kellermann et al., 2002, Curr OpinBiotechnol. 13:593-97, Russel et al., 2000, Infect Immun. 68:1820-26,Gallo et al., 2000, Eur J. Immun. 30:534-40, Davis et al., 1999, CancerMetastasis Rev. 18:421-25, Green, 1999, J Immunol Methods. 231:11-23,Jakobovits, 1998, Advanced Drug Delivery Reviews 31:33-42, Green et al.,1998, J Exp Med. 188:483-95, Jakobovits A, 1998, Exp. Opin. Invest.Drugs. 7:607-14, Tsuda et al., 1997, Genomics. 42:413-21, Mendez et al.,1997, Nat. Genet. 15:146-56, Jakobovits, 1994, Curr Biol. 4:761-63,Arbones et al., 1994, Immunity 1:247-60, Green et al., 1994, Nat. Genet.7:13-21, Jakobovits et al., 1993, Nature. 362:255-58, Jakobovits et al.,1993, Proc Natl Acad Sci USA. 90:2551-55. Chen, J., M. Trounstine, F. W.Alt, F. Young, C. Kurahara, J. Loring, D. Huszar “Immunoglobulin generearrangement in B cell deficient mice generated by targeted deletion ofthe JH locus.” International Immunology 5 (1993): 647-656, Choi et al.,1993, Nature Genetics 4: 117-23, Fishwild et al., 1996, NatureBiotechnology 14: 845-51, Harding et al., 1995, Annals of the New YorkAcademy of Sciences, Lonberg et al., 1994, Nature 368: 856-59, Lonberg,1994, Transgenic Approaches to Human Monoclonal Antibodies in Handbookof Experimental Pharmacology 113: 49-101, Lonberg et al., 1995, InternalReview of Immunology 13: 65-93, Neuberger, 1996, Nature Biotechnology14: 826, Taylor et al., 1992, Nucleic Acids Research 20: 6287-95, Tayloret al., 1994, International Immunology 6: 579-91, Tomizuka et al., 1997,Nature Genetics 16: 133-43, Tomizuka et al., 2000, Proceedings of theNational Academy of Sciences USA 97: 722-27, Tuaillon et al., 1993,Proceedings of the National Academy of Sciences USA 90: 3720-24, andTuaillon et al., 1994, Journal of Immunology 152: 2912-20.

In another aspect, the present invention provides monoclonal antibodiesthat bind to IL-21 receptor. Monoclonal antibodies may be produced usingany technique known in the art, e.g., by immortalizing spleen cellsharvested from the transgenic animal after completion of theimmunization schedule. The spleen cells can be immortalized using anytechnique known in the art, e.g., by fusing them with myeloma cells toproduce hybridomas. Myeloma cells for use in hybridoma-producing fusionprocedures preferably are non-antibody-producing, have high fusionefficiency, and enzyme deficiencies that render them incapable ofgrowing in certain selective media which support the growth of only thedesired fused cells (hybridomas). Examples of suitable cell lines foruse in mouse fusions include Sp-20, P3-X63/Ag8, P3-X63-Ag8.653, NS1/1.Ag4 1, Sp210-Ag14, FO, NSO/U, MPC-11, MPC11-X45-GTG 1.7 and S194/5XX0 Bul;examples of cell lines used in rat fusions include R210.RCY3, Y3-Ag1.2.3, IR983F and 4B210. Other cell lines useful for cell fusions areU-266, GM1500-GRG2, LICR-LON-HMy2 and UC729-6.

In one embodiment, a hybridoma cell line is produced by immunizing ananimal (e.g., a transgenic animal having human immunoglobulin sequences)with an IL-21 receptor immunogen; harvesting spleen cells from theimmunized animal; fusing the harvested spleen cells to a myeloma cellline, thereby generating hybridoma cells; establishing hybridoma celllines from the hybridoma cells, and identifying a hybridoma cell linethat produces an antibody that binds an IL-21 receptor polypeptide. Suchhybridoma cell lines, and anti-IL-21 receptor monoclonal antibodiesproduced by them, are encompassed by the present invention.

Monoclonal antibodies secreted by a hybridoma cell line can be purifiedusing any technique known in the art. Hybridomas or mAbs may be furtherscreened to identify mAbs with particular properties, such as theability to block an IL-21 induced activity. Examples of such screens areprovided in the examples below.

Molecular evolution of the complementarity determining regions (CDRs) inthe center of the antibody binding site also has been used to isolateantibodies with increased affinity, for example, antibodies havingincreased affinity for c-erbB-2, as described by Schier et al., 1996, J.Mol. Biol. 263:551. Accordingly, such techniques are useful in preparingantibodies to IL-21 receptor.

Antigen binding proteins directed against an IL-21 receptor can be used,for example, in assays to detect the presence of IL-21 receptorpolypeptides, either in vitro or in vivo. The antigen binding proteinsalso may be employed in purifying IL-21 receptor proteins byimmunoaffinity chromatography. Those antigen binding proteins thatadditionally can block binding of IL-21 to IL-21 receptor may be used toinhibit a biological activity that results from such binding. Blockingantigen binding proteins can be used in the methods of the presentinvention. Such antigen binding proteins that function as IL-21antagonists may be employed in treating any IL-21-induced condition,including but not limited to lupus, SLE, and arthritis. In oneembodiment, a human anti-IL-21 receptor monoclonal antibody generated byprocedures involving immunization of transgenic mice is employed intreating such conditions.

Antigen binding proteins may be employed in an in vitro procedure, oradministered in vivo to inhibit an IL-21-induced biological activity.Disorders caused or exacerbated (directly or indirectly) by theinteraction of IL-21 with cell surface IL-21 receptor, examples of whichare provided above, thus may be treated. In one embodiment, the presentinvention provides a therapeutic method comprising in vivoadministration of an IL-21 blocking antigen binding protein to a mammalin need thereof in an amount effective for reducing an IL-21-inducedbiological activity.

Antigen binding proteins of the invention include partially human andfully human monoclonal antibodies that inhibit a biological activity ofIL-21. One embodiment is directed to a human monoclonal antibody that atleast partially blocks binding of IL-21 to a cell that expresses humanIL-21 receptor. In one embodiment, the antibodies are generated byimmunizing a transgenic mouse with an IL-21 receptor immunogen. Inanother embodiment, the immunogen is a human IL-21 receptor polypeptide(e.g., a soluble fragment comprising all or part of the IL-21 receptorextracellular domain). Hybridoma cell lines derived from such immunizedmice, wherein the hybridoma secretes a monoclonal antibody that bindsIL-21 receptor, also are provided herein.

Although human, partially human, or humanized antibodies will besuitable for many applications, particularly those involvingadministration of the antibody to a human subject, other types ofantigen binding proteins will be suitable for certain applications. Thenon-human antibodies of the invention can be, for example, derived fromany antibody-producing animal, such as mouse, rat, rabbit, goat, donkey,or non-human primate (such as monkey (e.g., cynomologous or rhesusmonkey) or ape (e.g., chimpanzee)). Non-human antibodies of theinvention can be used, for example, in in vitro and cell-culture basedapplications, or any other application where an immune response to theantibody of the invention does not occur, is insignificant, can beprevented, is not a concern, or is desired. In one embodiment, anon-human antibody of the invention is administered to a non-humansubject. In another embodiment, the non-human antibody does not elicitan immune response in the non-human subject. In another embodiment, thenon-human antibody is from the same species as the non-human subject,e.g., a mouse antibody of the invention is administered to a mouse. Anantibody from a particular species can be made by, for example,immunizing an animal of that species with the desired immunogen (e.g., asoluble IL-21 receptor polypeptide) or using an artificial system forgenerating antibodies of that species (e.g., a bacterial or phagedisplay-based system for generating antibodies of a particular species),or by converting an antibody from one species into an antibody fromanother species by replacing, e.g., the constant region of the antibodywith a constant region from the other species, or by replacing one ormore amino acid residues of the antibody so that it more closelyresembles the sequence of an antibody from the other species. In oneembodiment, the antibody is a chimeric antibody comprising amino acidsequences derived from antibodies from two or more different species.

Antigen binding proteins may be prepared by any of a number ofconventional techniques. For example, they may be purified from cellsthat naturally express them (e.g., an antibody can be purified from ahybridoma that produces it), or produced in recombinant expressionsystems, using any technique known in the art. See, for example,Monoclonal Antibodies, Hybridomas: A New Dimension in BiologicalAnalyses, Kennet et al. (eds.), Plenum Press, New York (1980); andAntibodies: A Laboratory Manual, Harlow and Land (eds.), Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y., (1988).

Any expression system known in the art can be used to make therecombinant polypeptides of the invention. In general, host cells aretransformed with a recombinant expression vector that comprises DNAencoding a desired polypeptide. Among the host cells that may beemployed are prokaryotes, yeast or higher eukaryotic cells. Prokaryotesinclude gram negative or gram positive organisms, for example E. coli orbacilli. Higher eukaryotic cells include insect cells and establishedcell lines of mammalian origin. Examples of suitable mammalian host celllines include the COS-7 line of monkey kidney cells (ATCC CRL 1651)(Gluzman et al., 1981, Cell 23:175), L cells, 293 cells, C127 cells, 3T3cells (ATCC CCL 163), Chinese hamster ovary (CHO) cells, HeLa cells, BHK(ATCC CRL 10) cell lines, and the CV1/EBNA cell line derived from theAfrican green monkey kidney cell line CV1 (ATCC CCL 70) as described byMcMahan et al., 1991, EMBO J. 10: 2821. Appropriate cloning andexpression vectors for use with bacterial, fungal, yeast, and mammaliancellular hosts are described by Pouwels et al. (Cloning Vectors: ALaboratory Manual, Elsevier, New York, 1985).

The transformed cells can be cultured under conditions that promoteexpression of the polypeptide, and the polypeptide recovered byconventional protein purification procedures. One such purificationprocedure includes the use of affinity chromatography, e.g., over amatrix having all or a portion (e.g., the extracellular domain) of IL-21receptor bound thereto. Polypeptides contemplated for use herein includesubstantially homogeneous recombinant mammalian anti-IL-21 receptorantibody polypeptides substantially free of contaminating endogenousmaterials.

Antigen binding proteins may be prepared, and screened for desiredproperties, by any of a number of known techniques. Certain of thetechniques involve isolating a nucleic acid encoding a polypeptide chain(or portion thereof) of an antigen binding protein of interest (e.g., ananti-IL-21 receptor antibody), and manipulating the nucleic acid throughrecombinant DNA technology. The nucleic acid may be fused to anothernucleic acid of interest, or altered (e.g., by mutagenesis or otherconventional techniques) to add, delete, or substitute one or more aminoacid residues, for example.

In one aspect, the present invention provides antigen-binding fragmentsof an anti-IL-21 receptor antibody of the invention. Such fragments canconsist entirely of antibody-derived sequences or can compriseadditional sequences. Examples of antigen-binding fragments include Fab,F(ab′)2, single chain antibodies, diabodies, triabodies, tetrabodies,and domain antibodies. Other examples are provided in Lunde et al.,2002, Biochem. Soc. Trans. 30:500-06.

Single chain antibodies may be formed by linking heavy and light chainvariable domain (Fv region) fragments via an amino acid bridge (shortpeptide linker), resulting in a single polypeptide chain. Suchsingle-chain Fvs (scFvs) have been prepared by fusing DNA encoding apeptide linker between DNAs encoding the two variable domainpolypeptides (VL and VH). The resulting polypeptides can fold back onthemselves to form antigen-binding monomers, or they can form multimers(e.g., dimers, trimers, or tetramers), depending on the length of aflexible linker between the two variable domains (Kortt et al., 1997,Prot. Eng. 10:423; Kortt et al., 2001, Biomol. Eng. 18:95-108). Bycombining different VL and VH-comprising polypeptides, one can formmultimeric scFvs that bind to different epitopes (Kriangkum et al.,2001, Biomol. Eng. 18:31-40). Techniques developed for the production ofsingle chain antibodies include those described in U.S. Pat. No.4,946,778; Bird, 1988, Science 242:423; Huston et al., 1988, Proc. Natl.Acad. Sci. USA 85:5879; Ward et al., 1989, Nature 334:544, de Graaf etal., 2002, Methods Mol. Biol. 178:379-87. Single chain antibodiesderived from antibodies provided herein include, but are not limited to,scFvs comprising one or more variable domain sequences, or one or moreCDR sequences from one or more variable domain sequences, disclosedherein.

In some embodiments, antigen binding proteins (e.g., antibodies,antibody fragments, and antibody derivatives) of the invention comprisea light chain and/or a heavy chain antibody constant region. Anyantibody constant regions known in the art can be used. The light chainconstant region can be, for example, a kappa- or lambda-type light chainconstant region, e.g., a human kappa- or lambda-type light chainconstant region. The heavy chain constant region can be, for example, analpha-, delta-, epsilon-, gamma-, or mu-type heavy chain constantregions, e.g., a human alpha-, delta-, epsilon-, gamma-, or mu-typeheavy chain constant region. In one embodiment, the light or heavy chainconstant region is a fragment, derivative, variant, or mutein of anaturally occurring constant region.

Techniques are known for deriving an antibody of a different subclass orisotype from an antibody of interest, i.e., subclass switching. Thus,IgG antibodies may be derived from an IgM antibody, for example, andvice versa. Such techniques allow the preparation of new antibodies thatpossess the antigen-binding properties of a given antibody (the parentantibody), but also exhibit biological properties associated with anantibody isotype or subclass different from that of the parent antibody.Recombinant DNA techniques may be employed. Cloned DNA encodingparticular antibody polypeptides may be employed in such procedures,e.g., DNA encoding the constant domain of an antibody of the desiredisotype. See also Lantto et al., 2002, Methods Mol. Biol. 178:303-16.

Accordingly, the antigen binding proteins of the present inventioninclude those comprising, for example, one or more of the variabledomain sequences disclosed herein and having a desired isotype (forexample, IgA, IgG1, IgG2, IgG3, IgG4, IgM, IgE, and IgD), as well as Fabor F(ab′)2 fragments thereof. Moreover, if an IgG4 is desired, it mayalso be desired to introduce a point mutation (CPSCP (SEQ ID NO:2)->CPPCP (SEQ ID NO: 3)) in the hinge region as described in Bloom etal., 1997, Protein Science 6:407, incorporated by reference herein) toalleviate a tendency to form intra-H chain disulfide bonds that can leadto heterogeneity in the IgG4 antibodies.

Techniques for deriving antigen binding proteins having differentproperties (i.e., varying affinities for the antigen to which they bind)are also known. One such technique, referred to as chain shuffling,involves displaying immunoglobulin variable domain gene repertoires onthe surface of filamentous bacteriophage, often referred to as phagedisplay. Chain shuffling has been used to prepare high affinityantibodies to the hapten 2-phenyloxazol-5-one, as described by Marks etal., 1992, BioTechnology, 10:779.

In another embodiment, the present invention provides an antigen bindingprotein that has a low dissociation rate from IL-21 receptor. In oneembodiment, the antigen binding protein has a K_(off) of 1×10 s⁻¹ orlower. In another embodiment, the K_(off) is 5×10⁻⁵ s⁻¹ or lower. Inanother embodiment, the K_(off) is substantially the same as an antibodydisclosed herein. In another embodiment, the antigen binding proteinbinds to IL-21 receptor with substantially the same K_(off) as anantibody disclosed herein. In another embodiment, the antigen bindingprotein binds to IL-21 receptor with substantially the same K_(off) asan antibody that comprises one or more CDRs from an antibody disclosedherein.

In another aspect, the present invention provides an antigen bindingprotein having a half-life of at least one day in vitro or in vivo(e.g., when administered to a human subject). In one embodiment, theantigen binding protein has a half-life of at least three days. Inanother embodiment, the antigen binding protein has a half-life of fourdays or longer. In another embodiment, the antigen binding protein has ahalf-life of eight days or longer. In another embodiment, the antigenbinding protein is derivatized or modified such that it has a longerhalf-life as compared to the underivatized or unmodified antigen bindingprotein. In another embodiment, the antigen binding protein contains oneor more point mutations to increase serum half life, such as describedin WO 00/09560, published Feb. 24, 2000, incorporated by reference.

The present invention further provides multi-specific antigen bindingproteins, for example, bispecific antigen binding protein, e.g., antigenbinding protein that bind to two different epitopes of IL-21 receptor,or to an epitope of IL-21 receptor and an epitope of another molecule,via two different antigen binding sites or regions. Moreover, bispecificantigen binding protein as disclosed herein can comprise an IL-21receptor binding site from one of the herein-described antibodies and asecond IL-21 receptor binding region from another of theherein-described antibodies, including those described herein byreference to other publications. Alternatively, a bispecific antigenbinding protein may comprise an antigen binding site from one of theherein described antibodies and a second antigen binding site fromanother IL-21 receptor antibody that is known in the art, or from anantibody that is prepared by known methods or the methods describedherein.

Numerous methods of preparing bispecific antibodies are known in theart, and discussed in U.S. patent application Ser. No. 09/839,632, filedApr. 20, 2001 (incorporated by reference herein). Such methods includethe use of hybrid-hybridomas as described by Milstein et al., 1983,Nature 305:537, and others (U.S. Pat. No. 4,474,893, U.S. Pat. No.6,106,833), and chemical coupling of antibody fragments (Brennan et al.,1985, Science 229:81; Glennie et al., 1987, J. Immunol. 139:2367; U.S.Pat. No. 6,010,902). Moreover, bispecific antibodies can be produced viarecombinant means, for example by using leucine zipper moieties (i.e.,from the Fos and Jun proteins, which preferentially form heterodimers;Kostelny et al., 1992, J. Immunol. 148:1547) or other lock and keyinteractive domain structures as described in U.S. Pat. No. 5,582,996.Additional useful techniques include those described in Kortt et al.,1997, supra; U.S. Pat. No. 5,959,083; and U.S. Pat. No. 5,807,706.

In another aspect, the antigen binding protein of the present inventioncomprises a derivative of an antibody. The derivatized antibody cancomprise any molecule or substance that imparts a desired property tothe antibody, such as increased half-life in a particular use. Thederivatized antibody can comprise, for example, a detectable (orlabeling) moiety (e.g., a radioactive, colorimetric, antigenic orenzymatic molecule, a detecable bead (such as a magnetic or electrodense(e.g., gold) bead), or a molecule that binds to another molecule (e.g.,biotin or streptavidin)), a therapeutic or diagnostic moiety (e.g., aradioactive, cytotoxic, or pharmaceutically active moiety), or amolecule that increases the suitability of the antibody for a particularuse (e.g., administration to a subject, such as a human subject, orother in vivo or in vitro uses). Examples of molecules that can be usedto derivatize an antibody include albumin (e.g., human serum albumin)and polyethylene glycol (PEG). Albumin-linked and PEGylated derivativesof antibodies can be prepared using techniques well known in the art. Inone embodiment, the antibody is conjugated or otherwise linked totransthyretin (TTR) or a TTR variant. The TTR or TTR variant can bechemically modified with, for example, a chemical selected from thegroup consisting of dextran, poly(n-vinyl pyurrolidone), polyethyleneglycols, propropylene glycol homopolymers, polypropylene oxide/ethyleneoxide co-polymers, polyoxyethylated polyols and polyvinyl alcohols. USPat. App. No. 20030195154.

In another aspect, the present invention provides methods of screeningfor a molecule that binds to IL-21 receptor using the antigen bindingproteins of the present invention. Any suitable screening technique canbe used. In one embodiment, an IL-21 receptor molecule, or a fragmentthereof to which an antigen binding protein of the present inventionbinds, is contacted with the antigen binding protein of the inventionand with another molecule, wherein the other molecule binds to IL-21receptor if it reduces the binding of the antigen binding protein toIL-21 receptor. Binding of the antigen binding protein can be detectedusing any suitable method, e.g., an ELISA. Detection of binding of theantigen binding protein to IL-21 receptor can be simplified bydetectably labeling the antigen binding protein, as discussed above. Inanother embodiment, the IL-21 receptor-binding molecule is furtheranalyzed to determine whether it inhibits IL-21 receptor-mediatedsignaling.

Nucleic Acids

In one aspect, the present invention provides isolated nucleic acidmolecules. The nucleic acids comprise, for example, polynucleotides thatencode all or part of an antigen binding protein, for example, one orboth chains of an antibody of the invention, or a fragment, derivative,mutein, or variant thereof, polynucleotides sufficient for use ashybridization probes, PCR primers or sequencing primers for identifying,analyzing, mutating or amplifying a polynucleotide encoding apolypeptide, anti-sense nucleic acids for inhibiting expression of apolynucleotide, and complementary sequences of the foregoing. Thenucleic acids can be any length. They can be, for example, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 75, 100, 125, 150, 175, 200, 250, 300, 350,400, 450, 500, 750, 1,000, 1,500, 3,000, 5,000 or more nucleotides inlength, and/or can comprise one or more additional sequences, forexample, regulatory sequences, and/or be part of a larger nucleic acid,for example, a vector. The nucleic acids can be single-stranded ordouble-stranded and can comprise RNA and/or DNA nucleotides, andartificial variants thereof (e.g., peptide nucleic acids).

Nucleic acids encoding antibody polypeptides (e.g., heavy or lightchain, variable domain only, or full length) may be isolated fromB-cells of mice that have been immunized with IL-21 receptor. Thenucleic acid may be isolated by conventional procedures such aspolymerase chain reaction (PCR).

Representative nucleic acid sequences encoding some of the antibodies ofthe invention are disclosed herein. Particular nucleic acid sequencesencoding the variable domains of antibodies 10C2, 8B9, 8B9.13, 29G8,31C5, 29G2, 31E7, 34H7, 30G3, and 37G3 are provided in FIGS. 3 and 5.The skilled artisan will appreciate that, due to the degeneracy of thegenetic code, each of the polypeptide sequences disclosed herein isencoded by a large number of nucleic acid sequences. The presentinvention provides each degenerate nucleotide sequence encoding eachantigen binding protein or other polypeptide of the invention.

The invention further provides nucleic acids that hybridize to othernucleic acids (e.g., nucleic acids comprising a nucleotide sequencedisclosed herein) under particular hybridization conditions. Methods forhybridizing nucleic acids are well-known in the art. See, e.g., CurrentProtocols in Molecular Biology, John Wiley & Sons, N.Y. (1989),6.3.1-6.3.6. As defined herein, a moderately stringent hybridizationcondition uses a prewashing solution containing 5× sodiumchloride/sodium citrate (SSC), 0.5% SDS, 1.0 mM EDTA (pH 8.0),hybridization buffer of about 50% formamide, 6×SSC, and a hybridizationtemperature of 55° C. (or other similar hybridization solutions, such asone containing about 50% formamide, with a hybridization temperature of42° C.), and washing conditions of 60° C., in 0.5×SSC, 0.1% SDS. Astringent hybridization condition hybridizes in 6×SSC at 45° C.,followed by one or more washes in 0.1×SSC, 0.2% SDS at 68° C.Furthermore, one of skill in the art can manipulate the hybridizationand/or washing conditions to increase or decrease the stringency ofhybridization such that nucleic acids comprising nucleotide sequencesthat are at least 65, 70, 75, 80, 85, 90, 95, 98 or 99% identical toeach other typically remain hybridized to each other. The basicparameters affecting the choice of hybridization conditions and guidancefor devising suitable conditions are set forth by, for example,Sambrook, Fritsch, and Maniatis (1989, Molecular Cloning: A LaboratoryManual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.,chapters 9 and 11; and Current Protocols in Molecular Biology, 1995,Ausubel et al., eds., John Wiley & Sons, Inc., sections 2.10 and6.3-6.4), and can be readily determined by those having ordinary skillin the art based on, for example, the length and/or base composition ofthe DNA.

Changes can be introduced by mutation into a nucleic acid, therebyleading to changes in the amino acid sequence of a polypeptide (e.g., anantigen binding protein) that it encodes. Mutations can be introducedusing any technique known in the art. In one embodiment, one or moreparticular amino acid residues are changed using, for example, asite-directed mutagenesis protocol. In another embodiment, one or morerandomly selected residues is changed using, for example, a randommutagenesis protocol. However it is made, a mutant polypeptide can beexpressed and screened for a desired property (e.g., binding to IL-21receptor or blocking the binding of IL-21 to IL-21 receptor).

Mutations can be introduced into a nucleic acid without significantlyaltering the biological activity of a polypeptide that it encodes. Forexample, one can make nucleotide substitutions leading to amino acidsubstitutions at non-essential amino acid residues. In one embodiment, anucleotide sequence provided herein, or a desired fragment, variant, orderivative thereof, is mutated such that it encodes an amino acidsequence comprising one or more deletions, substitutions, or additionsof amino acid residues. In another embodiment, one or more mutations areintroduced into a nucleic acid that selectively change the biologicalactivity (e.g., binding of IL-21 receptor, inhibiting IL-21 binding,etc.) of a polypeptide that it encodes. For example, the mutation canquantitatively or qualitatively change the biological activity. Examplesof quantitative changes include increasing, reducing or eliminating theactivity. Examples of qualitative changes include changing the antigenspecificity of an antigen binding protein.

In another aspect, the present invention provides nucleic acid moleculesthat are suitable for use as primers or hybridization probes for thedetection of nucleic acid sequences of the invention. A nucleic acidmolecule of the invention can comprise only a portion of a nucleic acidsequence encoding a full-length polypeptide of the invention, forexample, a fragment that can be used as a probe or primer or a fragmentencoding an active portion (e.g., an IL-21 receptor binding portion) ofa polypeptide of the invention.

Probes based on the sequence of a nucleic acid of the invention can beused to detect the nucleic acid or similar nucleic acids, for example,transcripts encoding a polypeptide of the invention. The probe cancomprise a label group, e.g., a radioisotope, a fluorescent compound, anenzyme, or an enzyme co-factor. Such probes can be used to identify acell that expresses the polypeptide.

In another aspect, the present invention provides vectors comprising anucleic acid encoding a polypeptide of the invention or a portionthereof. Examples of vectors include, but are not limited to, plasmids,viral vectors, non-episomal mammalian vectors and expression vectors,for example, recombinant expression vectors.

The recombinant expression vectors of the invention can comprise anucleic acid of the invention in a form suitable for expression of thenucleic acid in a host cell. The recombinant expression vectors includeone or more regulatory sequences, selected on the basis of the hostcells to be used for expression, which is operably linked to the nucleicacid sequence to be expressed. Regulatory sequences include those thatdirect constitutive expression of a nucleotide sequence in many types ofhost cells (e.g., SV40 early gene enhancer, Rous sarcoma virus promoterand cytomegalovirus promoter), those that direct expression of thenucleotide sequence only in certain host cells (e.g., tissue-specificregulatory sequences, see Voss et al., 1986, Trends Biochem. Sci.11:287, Maniatis et al., 1987, Science 236:1237, incorporated byreference herein in their entireties), and those that direct inducibleexpression of a nucleotide sequence in response to particular treatmentor condition (e.g., the metallothionin promoter in mammalian cells andthe tet-responsive and/or streptomycin responsive promoter in bothprokaryotic and eukaryotic systems (see id.). It will be appreciated bythose skilled in the art that the design of the expression vector candepend on such factors as the choice of the host cell to be transformed,the level of expression of protein desired, etc. The expression vectorsof the invention can be introduced into host cells to thereby produceproteins or peptides, including fusion proteins or peptides, encoded bynucleic acids as described herein.

In another aspect, the present invention provides host cells into whicha recombinant expression vector of the invention has been introduced. Ahost cell can be any prokaryotic cell (for example, E. coli) oreukaryotic cell (for example, yeast, insect, or mammalian cells (e.g.,CHO cells)). Vector DNA can be introduced into prokaryotic or eukaryoticcells via conventional transformation or transfection techniques. Forstable transfection of mammalian cells, it is known that, depending uponthe expression vector and transfection technique used, only a smallfraction of cells may integrate the foreign DNA into their genome. Inorder to identify and select these integrants, a gene that encodes aselectable marker (e.g., for resistance to antibiotics) is generallyintroduced into the host cells along with the gene of interest.Preferred selectable markers include those which confer resistance todrugs, such as G418, hygromycin and methotrexate. Cells stablytransfected with the introduced nucleic acid can be identified by drugselection (e.g., cells that have incorporated the selectable marker genewill survive, while the other cells die), among other methods.

Methods of Making Anti-IL-21 Receptor Antigen Binding Proteins

A host cell comprising sequences that encode an anti-IL-21 receptorantigen binding protein of the invention can be used to make theanti-IL-21 receptor antigen binding protein. Typically, expressionvectors used in a host cell will contain sequences for plasmidmaintenance and for cloning and expression of exogenous nucleotidesequences. Such sequences, collectively referred to as “flankingsequences” in certain embodiments will typically include one or more ofthe following nucleotide sequences: a promoter, one or more enhancersequences, an origin of replication, a transcriptional terminationsequence, a complete intron sequence containing a donor and acceptorsplice site, a sequence encoding a leader sequence for polypeptidesecretion, a ribosome binding site, a polyadenylation sequence, apolylinker region for inserting the nucleic acid encoding thepolypeptide to be expressed, and a selectable marker element. Each ofthese sequences is discussed below.

Optionally, the vector may contain a “tag”-encoding sequence, i.e., anoligonucleotide molecule located at the 5′ or 3′ end of the anti-IL-21receptor antigen binding protein coding sequence(s); the oligonucleotidesequence encodes polyHis (such as hexaHis (SEQ ID NO: 4)), or another“tag” such as FLAG, HA (hemaglutinin influenza virus), or myc, for whichcommercially available antibodies exist. This tag is typically fused tothe polypeptide upon expression of the polypeptide, and can serve as ameans for affinity purification or detection of the anti-IL-21 receptorantigen binding protein from the host cell. Affinity purification can beaccomplished, for example, by column chromatography using antibodiesagainst the tag as an affinity matrix. Optionally, the tag cansubsequently be removed from the purified anti-IL-21 receptor antigenbinding protein polypeptide by various means such as using certainpeptidases for cleavage.

Flanking sequences may be homologous (i.e., from the same species and/orstrain as the host cell), heterologous (ie., from a species other thanthe host cell species or strain), hybrid (i.e., a combination offlanking sequences from more than one source), synthetic or native. Assuch, the source of a flanking sequence may be any prokaryotic oreukaryotic organism, any vertebrate or invertebrate organism, or anyplant, provided that the flanking sequence is functional in, and can beactivated by, the host cell machinery.

Flanking sequences useful in the vectors of this invention may beobtained by any of several methods well known in the art. Typically,flanking sequences useful herein will have been previously identified bymapping and/or by restriction endonuclease digestion and can thus beisolated from the proper tissue source using the appropriate restrictionendonucleases. In some cases, the full nucleotide sequence of a flankingsequence may be known. Here, the flanking sequence may be synthesizedusing the methods described herein for nucleic acid synthesis orcloning.

Whether all or only a portion of the flanking sequence is known, it maybe obtained using polymerase chain reaction (PCR) and/or by screening agenomic library with a suitable probe such as an oligonucleotide and/orflanking sequence fragment from the same or another species. Where theflanking sequence is not known, a fragment of DNA containing a flankingsequence may be isolated from a larger piece of DNA that may contain,for example, a coding sequence or even another gene or genes. Isolationmay be accomplished by restriction endonuclease digestion to produce theproper DNA fragment followed by isolation using agarose gelpurification, Qiagene® column chromatography (Chatsworth, Calif.), orother methods known to the skilled artisan. The selection of suitableenzymes to accomplish this purpose will be readily apparent to one ofordinary skill in the art.

An origin of replication is typically a part of those prokaryoticexpression vectors purchased commercially, and the origin aids in theamplification of the vector in a host cell. If the vector of choice doesnot contain an origin of replication site, one may be chemicallysynthesized based on a known sequence, and ligated into the vector. Forexample, the origin of replication from the plasmid pBR322 (New EnglandBiolabs, Beverly, Mass.) is suitable for most gram-negative bacteria,and various viral origins (e.g., SV40, polyoma, adenovirus, vesicularstomatitus virus (VSV), or papillomaviruses such as HPV or BPV) areuseful for cloning vectors in mammalian cells. Generally, the origin ofreplication component is not needed for mammalian expression vectors(for example, the SV40 origin is often used only because it alsocontains the virus early promoter).

A transcription termination sequence is typically located 3′ to the endof a polypeptide coding region and serves to terminate transcription.Usually, a transcription termination sequence in prokaryotic cells is aG-C rich fragment followed by a poly-T sequence. While the sequence iseasily cloned from a library or even purchased commercially as part of avector, it can also be readily synthesized using methods for nucleicacid synthesis such as those described herein.

A selectable marker gene encodes a protein necessary for the survivaland growth of a host cell grown in a selective culture medium. Typicalselection marker genes encode proteins that (a) confer resistance toantibiotics or other toxins, e.g., ampicillin, tetracycline, orkanamycin for prokaryotic host cells; (b) complement auxotrophicdeficiencies of the cell; or (c) supply critical nutrients not availablefrom complex or defined media. Preferred selectable markers are thekanamycin resistance gene, the ampicillin resistance gene, and thetetracycline resistance gene. Advantageously, a neomycin resistance genemay also be used for selection in both prokaryotic and eukaryotic hostcells.

Other selectable genes may be used to amplify the gene that will beexpressed. Amplification is the process wherein genes that are requiredfor production of a protein critical for growth or cell survival arereiterated in tandem within the chromosomes of successive generations ofrecombinant cells. Examples of suitable selectable markers for mammaliancells include dihydrofolate reductase (DHFR) and promoterless thymidinekinase genes. Mammalian cell transformants are placed under selectionpressure wherein only the transformants are uniquely adapted to surviveby virtue of the selectable gene present in the vector. Selectionpressure is imposed by culturing the transformed cells under conditionsin which the concentration of selection agent in the medium issuccessively increased, thereby leading to the amplification of both theselectable gene and the DNA that encodes another gene, such as anantibody that binds to IL-21 receptor polypeptide. As a result,increased quantities of a polypeptide such as an anti-IL-21 receptorantibody are synthesized from the amplified DNA.

A ribosome-binding site is usually necessary for translation initiationof mRNA and is characterized by a Shine-Dalgamo sequence (prokaryotes)or a Kozak sequence (eukaryotes). The element is typically located 3′ tothe promoter and 5′ to the coding sequence of the polypeptide to beexpressed.

In some cases, such as where glycosylation is desired in a eukaryotichost cell expression system, one may manipulate the various pre- orprosequences to improve glycosylation or yield. For example, one mayalter the peptidase cleavage site of a particular signal peptide, or addpro-sequences, which also may affect glycosylation. The final proteinproduct may have, in the −1 position (relative to the first amino acidof the mature protein) one or more additional amino acids incident toexpression, which may not have been totally removed. For example, thefinal protein product may have one or two amino acid residues found inthe peptidase cleavage site, attached to the amino-terminus.Alternatively, use of some enzyme cleavage sites may result in aslightly truncated form of the desired polypeptide, if the enzyme cutsat such area within the mature polypeptide.

Expression and cloning vectors of the invention will typically contain apromoter that is recognized by the host organism and operably linked tothe molecule encoding the anti-IL-21 receptor antigen binding protein.Promoters are untranscribed sequences located upstream (i.e., 5′) to thestart codon of a structural gene (generally within about 100 to 1000 bp)that control transcription of the structural gene. Promoters areconventionally grouped into one of two classes: inducible promoters andconstitutive promoters. Inducible promoters initiate increased levels oftranscription from DNA under their control in response to some change inculture conditions, such as the presence or absence of a nutrient or achange in temperature. Constitutive promoters, on the other hand,uniformly transcribe gene to which they are operably linked, that is,with little or no control over gene expression. A large number ofpromoters, recognized by a variety of potential host cells, are wellknown. A suitable promoter is operably linked to the DNA encoding heavychain or light chain comprising an anti-IL-21 receptor antigen bindingprotein of the invention by removing the promoter from the source DNA byrestriction enzyme digestion and inserting the desired promoter sequenceinto the vector.

Suitable promoters for use with yeast hosts are also well known in theart. Yeast enhancers are advantageously used with yeast promoters.Suitable promoters for use with mammalian host cells are well known andinclude, but are not limited to, those obtained from the genomes ofviruses such as polyoma virus, fowlpox virus, adenovirus (such asAdenovirus 2), bovine papilloma virus, avian sarcoma virus,cytomegalovirus, retroviruses, hepatitis-B virus and most preferablySimian Virus 40 (SV40). Other suitable mammalian promoters includeheterologous mammalian promoters, for example, heat-shock promoters andthe actin promoter.

Additional promoters which may be of interest include, but are notlimited to: SV40 early promoter (Benoist and Chambon, 1981, Nature290:304-10); CMV promoter (Thomsen et al., 1984, Proc. Natl. Acad. USA81:659-663); the promoter contained in the 3′ long terminal repeat ofRous sarcoma virus (Yamamoto, et al., 1980, Cell 22:787-97); herpesthymidine kinase promoter (Wagner et al., 1981, Proc. Natl. Acad. Sci.U.S.A. 78:144445); promoter and regulatory sequences from themetallothionine gene (Brinster et al., 1982, Nature 296:39-42); andprokaryotic promoters such as the beta-lactamase promoter(VIIIa-Kamaroff et al., 1978, Proc. Natl. Acad. Sci. U.S.A.,75:3727-31); or the tac promoter (DeBoer et al., 1983, Proc. Natl. Acad.Sci. U.S.A., 80:21-25). Also of interest are the following animaltranscriptional control regions, which exhibit tissue specificity andhave been utilized in transgenic animals: the elastase I gene controlregion that is active in pancreatic acinar cells (Swift et al., 1984,Cell 38:63946; Ornitz et al., 1986, Cold Spring Harbor Symp. Quant.Biol. 50:399409 (1986); MacDonald, 1987, Hepatology 7:425-515); theinsulin gene control region that is active in pancreatic beta cells(Hanahan, 1985, Nature 315:115-22); the immunoglobulin gene controlregion that is active in lymphoid cells (Grosschedl et al., 1984, Cell38:647-58; Adames et al., 1985, Nature 318:533-38; Alexander et al.,1987, Mol. Cell. Biol, 7:1436-44); the mouse mammary tumor virus controlregion that is active in testicular, breast, lymphoid and mast cells(Leder et al., 1986, Cell 45:485-95); the albumin gene control regionthat is active in liver (Pinkert et al., 1987, Genes and Devel.1:268-76); the alpha-feto-protein gene control region that is active inliver (Krumlauf et al., 1985, Mol. Cell. Biol., 5:1639-48; Hammer etal., 1987, Science 235:53-58); the alpha 1-antitrypsin gene controlregion that is active in liver (Kelsey et al., 1987, Genes and Devel.1:161-71); the beta-globin gene control region that is active in myeloidcells (Mogram et al., 1985, Nature 315:33840; Kollias et al., 1986, Cell46:89-94); the myelin basic protein gene control region that is activein oligodendrocyte cells in the brain (Readhead et al., 1987, Cell48:703-12); the myosin light chain-2 gene control region that is activein skeletal muscle (Sani, 1985, Nature 314:283-86); and the gonadotropicreleasing hormone gene control region that is active in the hypothalamus(Mason et al., 1986, Science 234:1372-78).

An enhancer sequence may be inserted into the vector to increasetranscription of DNA encoding light chain or heavy chain comprising ananti-IL-21 receptor antigen binding protein of the invention by highereukaryotes. Enhancers are cis-acting elements of DNA, usually about10-300 bp in length, that act on the promoter to increase transcription.Enhancers are relatively orientation and position independent, havingbeen found at positions both 5′ and 3′ to the transcription unit.Several enhancer sequences available from mammalian genes are known(e.g., globin, elastase, albumin, alpha-feto-protein and insulin).Typically, however, an enhancer from a virus is used. The SV40 enhancer,the cytomegalovirus early promoter enhancer, the polyoma enhancer, andadenovirus enhancers known in the art are exemplary enhancing elementsfor the activation of eukaryotic promoters. While an enhancer may bepositioned in the vector either 5′ or 3′ to a coding sequence, it istypically located at a site 5′ from the promoter.

A sequence encoding an appropriate native or heterologous signalsequence (leader sequence or signal peptide) can be incorporated into anexpression vector, to promote extracellular secretion of the antibody.The choice of signal peptide or leader depends on the type of host cellsin which the antibody is to be produced, and a heterologous signalsequence can replace the native signal sequence. Examples of signalpeptides that are functional in mammalian host cells include thefollowing: the signal sequence for interleukin-7 (IL-7) described inU.S. Pat. No. 4,965,195; the signal sequence for interleukin-2 receptordescribed in Cosman et al. (1984, Nature 312: 768); the interleukin-4receptor signal peptide described in EP Patent No. 0 367 566; the type Iinterleukin-1 receptor signal peptide described in U.S. Pat. No.4,968,607; the type II interleukin-1 receptor signal peptide describedin EP Patent No. 0 460 846; the signal sequence of human IgK; and thesignal sequence of human growth hormone.

Expression vectors of the invention may be constructed from a startingvector such as a commercially available vector. Such vectors may or maynot contain all of the desired flanking sequences. Where one or more ofthe flanking sequences described herein are not already present in thevector, they may be individually obtained and ligated into the vector.Methods used for obtaining each of the flanking sequences are well knownto one skilled in the art.

After the vector has been constructed and a nucleic acid moleculeencoding light chain, a heavy chain, or a light chain and a heavy chaincomprising an anti-IL-21 receptor antibody has been inserted into theproper site of the vector, the completed vector may be inserted into asuitable host cell for amplification and/or polypeptide expression. Thetransformation of an expression vector for an anti-IL-21 receptorantigen binding protein into a selected host cell may be accomplished bywell known methods including transfection, infection, calcium phosphateco-precipitation, electroporation, microinjection, lipofection,DEAE-dextran mediated transfection, or other known techniques. Themethod selected will in part be a function of the type of host cell tobe used.

A host cell, when cultured under appropriate conditions, synthesizes ananti-IL-21 receptor antigen binding protein that can subsequently becollected from the culture medium (if the host cell secretes it into themedium) or directly from the host cell producing it (if it is notsecreted). The selection of an appropriate host cell will depend uponvarious factors, such as desired expression levels, polypeptidemodifications that are desirable or necessary for activity (such asglycosylation or phosphorylation) and ease of folding into abiologically active molecule.

Mammalian cell lines available as hosts for expression are well known inthe art and include, but are not limited to, immortalized cell linesavailable from the American Type Culture Collection (ATCC), includingbut not limited to Chinese hamster ovary (CHO) cells, HeLa cells, babyhamster kidney (BHK) cells, monkey kidney cells (COS), humanhepatocellular carcinoma cells (e.g., Hep G2), and a number of othercell lines. In certain embodiments, cell lines may be selected throughdetermining which cell lines have high expression levels andconstitutively produce antibodies with IL-21 receptor bindingproperties. In another embodiment, a cell line from the B cell lineagethat does not make its own antibody but has a capacity to make andsecrete a heterologous antibody can be selected.

Formulations

In some embodiments, the invention provides pharmaceutical compositionscomprising a therapeutically effective amount of one or a plurality ofthe antibodies of the invention together with a pharmaceuticallyacceptable diluent, carrier, solubilizer, emulsifier, preservative,and/or adjuvant. Preferably, acceptable formulation materials arenontoxic to recipients at the dosages and concentrations employed. Inpreferred embodiments, pharmaceutical compositions comprising atherapeutically effective amount of anti-IL-21 receptor antibodies areprovided.

In certain embodiments, acceptable formulation materials preferably arenontoxic to recipients at the dosages and concentrations employed.

In certain embodiments, the pharmaceutical composition may containformulation materials for modifying, maintaining or preserving, forexample, the pH, osmolarity, viscosity, clarity, color, isotonicity,odor, sterility, stability, rate of dissolution or release, adsorptionor penetration of the composition. In such embodiments, suitableformulation materials include, but are not limited to, amino acids (suchas glycine, glutamine, asparagine, arginine or lysine); antimicrobials;antioxidants (such as ascorbic acid, sodium sulfite or sodiumhydrogen-sulfite); buffers (such as borate, bicarbonate, Tris-HCl,citrates, phosphates or other organic acids); bulking agents (such asmannitol or glycine); chelating agents (such as ethylenediaminetetraacetic acid (EDTA)); complexing agents (such as caffeine,polyvinylpyrrolidone, beta-cyclodextrin orhydroxypropyl-beta-cyclodextrin); fillers; monosaccharides;disaccharides; and other carbohydrates (such as glucose, mannose ordextrins); proteins (such as serum albumin, gelatin or immunoglobulins);coloring, flavoring and diluting agents; emulsifying agents; hydrophilicpolymers (such as polyvinylpyrrolidone); low molecular weightpolypeptides; salt-forming counterions (such as sodium); preservatives(such as benzalkonium chloride, benzoic acid, salicylic acid,thimerosal, phenethyl alcohol, methylparaben, propylparaben,chlorhexidine, sorbic acid or hydrogen peroxide); solvents (such asglycerin, propylene glycol or polyethylene glycol); sugar alcohols (suchas mannitol or sorbitol); suspending agents; surfactants or wettingagents (such as pluronics, PEG, sorbitan esters, polysorbates such aspolysorbate 20, polysorbate 80, triton, tromethamine, lecithin,cholesterol, tyloxapal); stability enhancing agents (such as sucrose orsorbitol); tonicity enhancing agents (such as alkali metal halides,preferably sodium or potassium chloride, mannitol sorbitol); deliveryvehicles; diluents; excipients and/or pharmaceutical adjuvants. SeeREMINGTON'S PHARMACEUTICAL SCIENCES, 18th Edition, (A. R. Gennaro, ed.),1990, Mack Publishing Company.

In certain embodiments, the optimal pharmaceutical composition will bedetermined by one skilled in the art depending upon, for example, theintended route of administration, delivery format and desired dosage.See, for example, REMINGTON′S PHARMACEUTICAL SCIENCES, supra. In certainembodiments, such compositions may influence the physical state,stability, rate of in vivo release and rate of in vivo clearance of theantibodies of the invention.

In certain embodiments, the primary vehicle or carrier in apharmaceutical composition may be either aqueous or non-aqueous innature. For example, a suitable vehicle or carrier may be water forinjection, physiological saline solution or artificial cerebrospinalfluid, possibly supplemented with other materials common in compositionsfor parenteral administration. Neutral buffered saline or saline mixedwith serum albumin are further exemplary vehicles. In preferredembodiments, pharmaceutical compositions comprise Tris buffer of aboutpH 7.0-8.5, or acetate buffer of about pH 4.0-5.5, and may furtherinclude sorbitol or a suitable substitute therefor. In certainembodiments of the invention, anti-IL-21 receptor antigen bindingprotein compositions may be prepared for storage by mixing the selectedcomposition having the desired degree of purity with optionalformulation agents (REMINGTON′S PHARMACEUTICAL SCIENCES, supra) in theform of a lyophilized cake or an aqueous solution. Further, in certainembodiments, the, anti-IL-21 receptor antigen binding protein productmay be formulated as a lyophilizate using appropriate excipients such assucrose.

The pharmaceutical compositions of the invention can be selected forparenteral delivery. Alternatively, the compositions may be selected forinhalation or for delivery through the digestive tract, such as orally.Preparation of such pharmaceutically acceptable compositions is withinthe skill of the art.

The formulation components are present preferably in concentrations thatare acceptable to the site of administration. In certain embodiments,buffers are used to maintain the composition at physiological pH or at aslightly lower pH, typically within a pH range of from about 5 to about8.

When parenteral administration is contemplated, the therapeuticcompositions for use in this invention may be provided in the form of apyrogen-free, parenterally acceptable aqueous solution comprising thedesired anti-IL-21 receptor antigen binding protein in apharmaceutically acceptable vehicle. A particularly suitable vehicle forparenteral injection is sterile distilled water in which the, anti-IL-21receptor antigen binding protein is formulated as a sterile, isotonicsolution, properly preserved. In certain embodiments, the preparationcan involve the formulation of the desired molecule with an agent, suchas injectable microspheres, bio-erodible particles, polymeric compounds(such as polylactic acid or polyglycolic acid), beads or liposomes, thatmay provide controlled or sustained release of the product which can bedelivered via depot injection. In certain embodiments, hyaluronic acidmay also be used, having the effect of promoting sustained duration inthe circulation. In certain embodiments, implantable drug deliverydevices may be used to introduce the desired antibody molecule.

Pharmaceutical compositions of the invention can be formulated forinhalation. In these embodiments, anti-IL-21 receptor antigen bindingproteins are advantageously formulated as a dry, inhalable powder. Inpreferred embodiments, anti-IL-21 receptor antigen binding proteininhalation solutions may also be formulated with a propellant foraerosol delivery. In certain embodiments, solutions may be nebulizedPulmonary administration and formulation methods therefore are furtherdescribed in International Patent Application No. PCT/US94/001875, whichis incorporated by reference and describes pulmonary delivery ofchemically modified proteins.

It is also contemplated that formulations can be administered orally.Anti-IL-21 receptor antigen binding proteins that are administered inthis fashion can be formulated with or without carriers customarily usedin the compounding of solid dosage forms such as tablets and capsules.In certain embodiments, a capsule may be designed to release the activeportion of the formulation at the point in the gastrointestinal tractwhen bioavailability is maximized and pre-systemic degradation isminimized. Additional agents can be included to facilitate absorption ofthe anti-IL-21 receptor antigen binding protein. Diluents, flavorings,low melting point waxes, vegetable oils, lubricants, suspending agents,tablet disintegrating agents, and binders may also be employed.

A pharmaceutical composition of the invention is preferably provided tocomprise an effective quantity of one or a plurality of anti-IL-21receptor antigen binding proteins in a mixture with non-toxic excipientsthat are suitable for the manufacture of tablets. By dissolving thetablets in sterile water, or another appropriate vehicle, solutions maybe prepared in unit-dose form. Suitable excipients include, but are notlimited to, inert diluents, such as calcium carbonate, sodium carbonateor bicarbonate, lactose, or calcium phosphate; or binding agents, suchas starch, gelatin, or acacia; or lubricating agents such as magnesiumstearate, stearic acid, or talc.

Additional pharmaceutical compositions will be evident to those skilledin the art, including formulations involving anti-IL-21 receptor antigenbinding proteins in sustained- or controlled-delivery formulations.Techniques for formulating a variety of other sustained- orcontrolled-delivery means, such as liposome carriers, bio-erodiblemicroparticles or porous beads and depot injections, are also known tothose skilled in the art. See, for example, International PatentApplication No. PCT/US93/00829, which is incorporated by reference anddescribes controlled release of porous polymeric microparticles fordelivery of pharmaceutical compositions. Sustained-release preparationsmay include semipermeable polymer matrices in the form of shapedarticles, e.g. films, or microcapsules. Sustained release matrices mayinclude polyesters, hydrogels, polylactides (as disclosed in U.S. Pat.No. 3,773,919 and European Patent Application Publication No. EP 058481,each of which is incorporated by reference), copolymers of L-glutamicacid and gamma ethyl-L-glutamate (Sidman et al., 1983, Biopolymers22:547-556), poly (2-hydroxyethyl-methacrylate) (Langer et al., 1981, J.Biomed. Mater. Res. 15:167-277 and Langer, 1982, Chem. Tech. 12:98-105),ethylene vinyl acetate (Langer et al., supra) orpoly-D(−)-3-hydroxybutyric acid (European Patent Application PublicationNo. EP 133,988). Sustained release compositions may also includeliposomes that can be prepared by any of several methods known in theart. See e.g., Eppstein et al., 1985, Proc. Natl. Acad. Sci. USA82:3688-3692; European Patent Application Publication Nos. EP 036,676;EP 088,046 and EP 143,949, incorporated by reference.

Pharmaceutical compositions used for in vivo administration aretypically provided as sterile preparations. Sterilization can beaccomplished by filtration through sterile filtration membranes. Whenthe composition is lyophilized, sterilization using this method may beconducted either prior to or following lyophilization andreconstitution. Compositions for parenteral administration can be storedin lyophilized form or in a solution. Parenteral compositions generallyare placed into a container having a sterile access port, for example,an intravenous solution bag or vial having a stopper pierceable by ahypodermic injection needle.

Once the pharmaceutical composition has been formulated, it may bestored in sterile vials as a solution, suspension, gel, emulsion, solid,crystal, or as a dehydrated or lyophilized powder. Such formulations maybe stored either in a ready-to-use form or in a form (e.g., lyophilized)that is reconstituted prior to administration.

The invention also provides kits for producing a single-doseadministration unit. The kits of the invention may each contain both afirst container having a dried protein and a second container having anaqueous formulation. In certain embodiments of this invention, kitscontaining single and multi-chambered pre-filled syringes (e.g., liquidsyringes and lyosyringes) are provided.

Indications

The methods and compositions of the present invention (including, forexample, anti-IL-21 receptor antigen binding proteins, antibodies,antibody fragments, antibody derivatives, and other molecules of thepresent invention) can be used to treat a wide range of diseases,conditions, and indications. IL-21 has been shown to be essential forT-dependent antibody production in vitro (Kuchen at al. (2007) J Immunol179:5886) and may contribute to the overproduction of interferon-gamma(“IFN-γ”) in SLE patients (Harigai et al. (2008) J Immunol 181: 2211)and stimulates other pro-inflammatory effector mechanisms and moleculesthat are associated with a variety of autoimmune and/or inflammatoryconditions, including, for example, SLE (Bauer et al. (2006), PLoS Med.2(12): 2274-2284; Armarianzas et al. (2009), IEEE Transactions onInform. Tech. in Biomed. 13(3): 341-350), systemic sclerosis (Sozzani etal. (2010), Autoimmunity 43(3): 196-203), alopecia greata (Ghoreishi etal. (2010), Br. J. Dermatol. 163: 57-62), Graves' disease (Ruiz-R101 etal. (2011), J. Autoimmunity 36: 189-200), immune-ossious dysplasiaspondyloenchondrodysplasia (SPENCD) (Briggs et al. (2011), Nat. Gen.43(2): 127-132), Degos disease (Magro et al. (2011), Am. J. Clin.Pathol. 135: 599-610), Sjogren's syndrome (Sozzani et al. (2010),Autoimmunity 43(3): 196-203; Emamian et al. (2009), Genes Immun. 10:285-296), antiphospholipid syndrome (Armarianzas et al. (2009), IEEETransactions on Inform. Tech. in Biomed. 13(3): 341-350), inflammatorybowel diseases including Crohn's disease and ulcerative colitis (see,e.g., U.S. Pat. No. 6,558,661), rheumatoid arthritis (Dawidowicz et al.(2011), Ann. Rheum. Dis. 70: 117-121), Chagas disease cardiomyopathy(Cunha-Neto (2010), Autoimmunity Rev. 10: 163-165), psoriasis (Pietrzaket al. (2008), Clin. Chim. Acta 394: 7-21), multiple sclerosis (vanBaarsen et al. (2006), Genes and Immunity 7: 522-531), dermatomyositis(Somani et al. (2008), Arch. Dermatol. 145(4): 1341-1349), polimyositis(Sozzani et al. (2010), Autoimmunity 43(3): 196-203) panniculitis-likeT-cell lymphoma (Maliniemi et al. (2010), J. Invest, Dermatol. 130; S54(abstract 320)), type I diabetes (Reynier et al. (2010), Genes Immun.11: 269-278), sarcoidosis (Lee et al. 2011, Ann. Dermatol. 23(2):239-241; Kriegova et al. (2011), Eur. Respir. J. 38: 1136-1144), andhemophagocytic lymphohistiocytosis (HLH; Schmid et al. (2009), EMBOMolec. Med. 1(2): 112-124).

SLE is an autoimmune disease of unknown etiology marked byautoreactivity to nuclear self antigens. Its clinical manifestations areso diverse that it is questionable whether it is truly a single diseaseor a group of related conditions (Kotzin (1996) Cell 85:303; Rahman etal. (2008) N. Engl. J. Med. 358:929). Symptoms can include thefollowing: constitutional symptoms such as malaise, fatigue, fevers,anorexia, and weight loss; diverse skin symptoms including acute,transient facial rashes in adults, bullous disease, and chronic anddisfiguring rashes of the head and neck; arthritis; muscle pain and/orweakness; cardiovascular symptoms such as mitral valve thickening,vegetations, regurgitation, stenosis, pericarditis, and ischemic heartdisease, some of which can culminate in stroke, embolic disease, heartfailure, infectious endocarditis, or valve failure; nephritis, which isthe major cause of morbidity in SLE; neurological symptoms includingcognitive dysfunction, depression, psychosis, coma, seizure disorders,migraine, and other headache syndromes, aseptic meningitis, chorea,stroke, and cranial neuropathies; hemotologic symptoms includingleucopenia, thrombocytopenia, serositis, anemia, coagulationabnormalities, splenomegaly, and lymphadenopathy, variousgastrointestinal abnormalities, and even death (Vratsanos et al.,“Systemic Lupus Erythematosus,” Chapter 39 in Samter's ImmunologicalDiseases, 6th Edition, Austen et al., eds., Lippincott Williams &Wilkins, Philadelphia, Pa., 2001). In one embodiment, the compositionsand/or methods of the present invention are used to treat, reduce,ameliorate, eliminate or prevent one or more of these symptoms in apatient thought to have SLE.

Severity of symptoms varies widely, as does the course of the disease.The disease activity of SLE patients can be rated using an instrumentsuch as the Systemic Lupus Erythrmatosus Disease Activity Index(SELDAI), which provides a score for disease activity based on a scorethat takes into consideration the following symptoms, which are weightedaccording to clinicians' opinion of their importance: seizure,psychosis, organic brain syndrome, visual disturbance, cranial nervedisorder, lupus headache, vasculitis, arthritis, myositis, urinarycasts, hematuria, proteinuria, pyuria, new rash, alopecia, mucosalulcers, pleurisy, pericarditis, low complement, increased DNA binding,fever, thrombocytopenia, and leucopenia (Bombardier et al. (1992),Arthr. & Rheum. 35:630), the relevant portions of which are incorporatedherein by reference. The treatments described herein can be useful inlessening or eliminating symptoms of SLE as measured by SELDAI.

Another method for assessing disease activity in SLE is British IslesLupus Assessment Group (BILAG) index, which is a disease activityassessment system for SLE patients based on the principle of thephysician's intention to treat (Stoll et al. (1996) Ann. Rheum Dis. 55:756-760; Hay et al. (1993) Q. J. Med. 86:447). The portions of thesereferences describing the BILAG are incorporated herein by reference. ABILAG score is assigned by giving separate numeric or alphabetic diseaseactivity scores in each of eight organ-based systems, general (such asfever and fatigue), mucocutaneous (such as rash and alopecia, among manyother symptoms), neurological (such as seizures, migraine headaches, andpsychosis, among many other symptoms), musculoskeletal (such asarthritis), cardiorespiratory (such as cardiac failure and decreasedpulmonary function), vasculitis and thrombosis, renal (such asnephritis), and hematological. The compositions and/or methods describedherein can be useful in lessening or eliminating symptoms of SLE asmeasured by the BILAG index.

Discoid lupus is a particular form of chronic cutaneous lupus in whichthe patient has circular lesions that occur most commonly in sun-exposedareas. The lesions can leave disfiguring scars. Up to about 25% of SLEpatients develop discoid lupus lesions at some point in the course oftheir disease. These lesions may occur in patients that have no othersymptoms of SLE. The symptoms that relate specifically to skin incutaneous forms of lupus can be scored using the Cutaneous LupusErythematosus Disease Area and Severity Index (CLASI), which takes intoconsideration both disease activity (including erythema, scaling, andhypertrophy of the skin in various areas, as well as mucus membranelesions and alopecia) and disease-related damage (includingdyspigmentation, scarring, atrophy, and panniculitis of the skin as wellas scarring of the scalp). Such symptoms can be affected by a treatmentfor discoid lupus with an IL-21 receptor inhibitor. The CLASI isdescribed in detail by Albrecht et al. (2005) J. Invest. Dermatol.125:889. The portions of this article that describe what the CLASI is,what symptoms are included in it, and how to use it are incorporatedherein by reference. The treatments described herein can be useful forlessening or eliminating symptoms of discoid lupus as measured by theCLASI.

Another cutaneous disease that can be mediated by IL-21 receptor ispsoriasis. Symptoms of psoriasis include itchy, dry skin that can bepink/red in color, thickened and covered with flakes. It is a commoncondition and is episodic in nature, that is, patients can experienceflares and periods of remission. There are five type of psoriasis:erythrodermic, guttate, inverse, plaque, and pustular. Plaque psoriasisis the most common type.

The severity of disease in psoriasis patients can be measured in avariety of ways. One way disease activity is commonly measured inclinical trials the PASI score. A PASI score can range from 0 to 72,with 72 being the most severe disease. For purposes of PASI assessment,the body is considered to consist of four sections, legs, torso (thatis, stomach, chest, back, etc.), arms, and head, which are considered tohave 40%, 30%, 20%, and 10% of a person's skin, respectively. For eachsection, the percent of the area of skin affected is estimated andtransformed into a grade of from 0 to 6, with 0 being no affected skinand 6 being 90-100% of the skin of the body section in question beingaffected. The severity of disease is scored by separately consideringthree features of the affected skin, redness (erythema), scaling, andthickness, and assigning a severity score of from 0 to 4 for eachfeature for each body section. The sum of the severity scores for allthree features for each body section is calculated, and this sum ismultiplied by the weight of the respective section as determined by howmuch of the total skin that body section contains and by the percent ofthe body section affected. After this number is calculated for each bodysection, these numbers are added to yield the PASI score. Thus, the PASIscore can be expressed as follows:

PASI = 0.1(score  for  percent  of  the  head  affected)(sum  of  3  severity  scores  for  the  head) + 0.2(score  for  percent  of  the  arms  affected)(sum  of  3  severity  scores  for   the  arms) + 0.3(score  for  percent  of  the  torso  affected)(sum  of  3  severity  scores  for  the  torso) + 0.4(score  for  percent  of  the  legs  affected)(sum  of  3  severity  scores  for  the  legs)

The descriptions of PASI scores in the following two references areincorporated by reference herein: Feldman et al. (2005) Ann. Rheum. Dis.64:68 and Langley et al. (2004), J. Am. Acad. Dermatol. 51:563.

Many clinical trials refer to changes in PASI score over the course ofthe study. For example, a PASI 75 at a particular time point in aclinical trial means that the PASI score of a patient has decreased by75% as compared to that patient's PASI score at baseline. Similarly aPASI 50 or a PASI 90 denotes a 50% or 90% reduction in PASI score.

Another commonly used measure of psoriasis severity in clinical trialsis the static Physicians Global Assessment (sPGA). The sPGA is typicallya six category scale rating ranging from 0=none to 5=severe. ENBREL®(etanercept; Amgen Inc., Thousand Oaks, Calif.), Package Insert, 2008. AsPGA score of “clear” or “minimal” (sometimes alternately referred to as“almost clear”) requires no or minimal elevation of plaques, no or onlyvery faint redness, and no scaling or minimal scaling over <5% of thearea of the plaques. ENBREL® (etanercept), Package Insert, 2008. Theindividual elements of psoriasis plaque morphology or degree of bodysurface area involvement are not quantified. Nonetheless, sPGA scorescorrelate to some extent with PASI scores (Langley et al. (2004), J. Am.Acad. Dermatol. 51:563). In one embodiment, methods and/or compositionsdescribed herein lessen, eliminate or prevent psoriasis symptoms asmeasured by a PASI or an sPGA score.

Multiple sclerosis (MS) is an autoimmune disease characterized by damageto the myelin sheath that surrounds nerves, which leads to inhibition ortotal blockage of nerve impulses. The disease is very heterogeneous inclinical presentation, and there is a wide variation in response totreatment as well (van Baarsen et al. (2006) Genes and Immunity 7:522).Environmental factors, possibly viral infection, as well as geneticsusceptibility, are thought to play a role in causing MS. Symptoms caninclude loss of balance, muscle spasms, tremors, weakness, loss ofability to walk, loss of coordination, various bowel and bladderproblems, numbness, pain, tingling, slurred speech, difficulty chewingand swallowing, double vision, loss of vision, uncontrollable eyemovements, and depression, among many other possible symptoms. In manypatients episodes in which symptoms occur are interspersed with longperiods of remission. The methods described herein can lessen, eliminateor prevent one or more symptoms of MS.

Type I diabetes is an autoimmune disease resulting in the destruction ofinsulin-producing β-cells in the pancreas, which leads to a lack ofinsulin. Antibodies against β-cell epitopes are detected in the sera ofpre-diabetic patients, suggesting that there is an autoimmune process inprogress during a long asymptomatic period that precedes the onset ofclinical symptoms (Reynier et al. (2010) Genes and Immunity 11:269). Thelack of insulin leads to high glucose levels in the blood and urinecausing a variety of symptoms including frequent urination, increasedhunger and thirst, fatigue, and weight loss. It is generally treatedwith insulin, a treatment that must be continued indefinitely. Thecauses of type I diabetes are not completely clear, but are thought toinclude a genetic component. About thirty percent of non-diabeticsiblings of diabetic patients are found to express high levels of RNAsencoded by a group genes activated by type I interferon, althoughdiabetic patients do not overexpress these RNAs. Such overexpression maybe an indication of future disease. The methods described herein may beuseful to treat or prevent type I diabetes before and/or after the onsetof clinical symptoms.

IL-21 receptor activity is also implicated in Inflammatory boweldiseases (IBDs) such as Crohn's disease and ulcerative colitis. Crohn'sdisease is chronic and debilitating inflammatory bowel disease that isthought to reflect a overly-active TH1-mediated immune response to theflora of the gut. The lesions of Crohn's disease can appear anywhere inthe bowel and occasionally elsewhere in the gastrointestinal tract.Ulcerative colitis lesions, on the other hand, usually appear in thecolon. The nature of the lesions is also different, but the diseases aresufficiently similar that is sometimes difficult to distinguish themclinically. See, e.g., U.S. Pat. No. 6,558,661.

Evidence indicates that IL-21 receptor plays a role in IBDs. ElevatedIL-21 and IL-21 receptor levels were found in biopsies taken from IBDpatients and IL-21 was found to promote expression of inflammatorymediators in inflamed tissue explants cultures (Monteleone, 2005,Gastroenterology 128:687; Monteleone, 2006, Gut 55:1774). Thecompositions and methods described herein can be used to treat IBDpatients, and/or reduce, prevent, or eliminate one or more symptoms ofIBD.

Sarcoidosis is a systemic granulomatous disease that can affectessentially any tissue, but it primarily affects the lung and lymphaticsystems. It is characterized by the presence of noncaseating epithelioidcell granulomas in more than one organ system. Most commonly thegranulomas are found in lung, lymph nodes, skin, liver, and/or spleen,among other possible sites. It can be fatal. For example, fibrosis ofthe lungs can lead to fatality (Carter and Hunninghake, “Sarcoidosis,”Chapter 47 in Samter's Immunological Diseases, 6th Edition, Austen etal., eds., Lippincott Williams & Wilkins, Philadelphia, Pa., 2001). Thecompositions and/or methods described herein can be used to treatsarcoidosis patients, and/or to reduce, eliminate, or prevent symptomsof sarcoidosis.

Hemophagocytic lymphohistiocytosis (HLH) is a rare and often fataldisease having clinical manifestations including fever,hepatosplenomegaly, lymphadenopathy, jaundice and rash. Laboratoryfindings associated with HLH include lymphocytosis and histiocytosis andthe pathologic finding of hemophagocytosis. Pancytopenia, elevated serumferritin levels, and abnormal liver enzymes are also frequently present.The compositions and/or methods described herein can be used to treatHLH patients and/or to reduce, eliminate, or prevent symptoms of HLH.

Rheumatoid arthritis (RA) is a common inflammatory disease of synovialjoints and is characterized by the productin of pro-inflammaatorycytokines/mediators by immune cells that infiltrate synovium. Thiscauses proliferation of synovial fibroblasts, further release cytokineinflammatory molecules and formation of pannus tissue that eventuallydegrades cartilage and subchondral bone, leading to joint destructin,pain and disability. The compositions and/or methods described hereincan be used to treat RA patients and/or to reduce, eliminate, or preventsymptoms of RA.

Therapeutic Methods and Administration of Antigen Binding Proteins

In one aspect, the present invention provides methods of treating asubject. The method can, for example, have a generally salubrious effecton the subject, e.g., it can increase the subject's expected longevity.Alternatively, the method can, for example, treat, prevent, cure,relieve, or ameliorate (“treat”) a disease, disorder, condition, orillness (“a condition”). Among the conditions to be treated inaccordance with the present invention are conditions characterized byinappropriate expression or activity of IL-21 receptor and/or IL-21. Insome such conditions, the expression or activity level is too high, andthe treatment comprises administering an IL-21 receptor antagonist asdescribed herein. In other such conditions, the expression or activitylevel is too low, and the treatment comprises administering an IL-21receptor agonist as described herein. In other such conditions, thelevels of IL-21 receptor and/or IL-21 activity are not necessarilyelevated, but the subject is more sensitive to them.

In another aspect, the present invention provides methods of identifyingsubjects who are more likely to benefit from treatment using thecompositions and/or methods of treatment of the present invention. Suchmethods can enable a caregiver to better tailor a therapeutic regimen toa particular subject's needs and reduce the likelihood of an ineffectiveor counterproductive course of treatment. In one embodiment, the presentinvention provides a method of determining whether a subject is acandidate for treatment using a composition or method as describedherein comprising determining whether a target cell type in the subjectexpresses IL-21 receptor, wherein if the target cell type expressesIL-21 receptor, then the subject is a candidate for treatment. Inanother embodiment, the method comprises determining the approximateaverage number of IL-21 receptor molecules per target cell, wherein 10²,10³, 10⁴, 10⁵, or 10⁶ IL-21 receptor per cell indicates that the subjectis a candidate for treatment. The approximate average number of IL-21receptor molecules per target cell can be determined using any techniqueknown in the art, for example, by staining a sample comprising cells ofthe target cell type with an IL-21 receptor binding molecule, anddetecting the amount of IL-21 receptor binding molecule bound to thesample, where the amount of IL-21 receptor binding molecule detected isproportional to the average number of IL-21 receptor molecules in thesample. In another embodiment, the method comprises comparing theapproximate average number of IL-21 receptor molecules per target cellto a reference standard, wherein if the approximate average number ofIL-21 receptor molecules per target cell is greater than the referencestandard, then the subject is more likely to benefit from treatmentusing the compositions and/or methods of treatment of the presentinvention. In another aspect, the method comprises determining whetherIL-21 is present at elevated levels in the tissue of interest, e.g., inthe vicinity of immune cells expressing IL-21 receptor. In anotheraspect, the method comprises determining whether a molecule downstreamof IL-21 receptor is altered or activated in an IL-21 receptor-dependentfashion. Examples of such downstream molecules are STAT3, STAT1, STAT5,JAK1, and JAK3.

Certain methods provided herein comprise administering an IL-21 receptorbinding antigen binding protein to a subject, thereby reducing anIL-21-induced biological response that plays a role in a particularcondition. In particular embodiments, methods of the invention involvecontacting endogenous IL-21 receptor with an IL-21 receptor bindingantigen binding protein, e.g., via administration to a subject or in anex vivo procedure.

The term “treatment” encompasses alleviation or prevention of at leastone symptom or other aspect of a disorder, or reduction of diseaseseverity, and the like. An antigen binding protein need not effect acomplete cure, or eradicate every symptom or manifestation of a disease,to constitute a viable therapeutic agent. As is recognized in thepertinent field, drugs employed as therapeutic agents may reduce theseverity of a given disease state, but need not abolish everymanifestation of the disease to be regarded as useful therapeuticagents. Similarly, a prophylactically administered treatment need not becompletely effective in preventing the onset of a condition in order toconstitute a viable prophylactic agent. Simply reducing the impact of adisease (for example, by reducing the number or severity of itssymptoms, or by increasing the effectiveness of another treatment, or byproducing another beneficial effect), or reducing the likelihood thatthe disease will occur or worsen in a subject, is sufficient. Oneembodiment of the invention is directed to a method comprisingadministering to a patient an IL-21 receptor antagonist in an amount andfor a time sufficient to induce a sustained improvement over baseline ofan indicator that reflects the severity of the particular disorder.

As is understood in the pertinent field, pharmaceutical compositionscomprising the molecules of the invention are administered to a subjectin a manner appropriate to the indication. Pharmaceutical compositionsmay be administered by any suitable technique, including but not limitedto parenterally, topically, or by inhalation. If injected, thepharmaceutical composition can be administered, for example, viaintra-articular, intravenous, intramuscular, intralesional,intraperitoneal or subcutaneous routes, by bolus injection, orcontinuous infusion. Localized administration, e.g. at a site of diseaseor injury is contemplated, as are transdermal delivery and sustainedrelease from implants. Delivery by inhalation includes, for example,nasal or oral inhalation, use of a nebulizer, inhalation of theantagonist in aerosol form, and the like. Other alternatives includeeyedrops; oral preparations including pills, syrups, lozenges or chewinggum; and topical preparations such as lotions, gels, sprays, andointments.

Use of antigen binding proteins in ex vivo procedures also iscontemplated. For example, a patient's blood or other bodily fluid maybe contacted with an antigen binding protein that binds IL-21 receptorex vivo. The antigen binding protein may be bound to a suitableinsoluble matrix or solid support material.

Advantageously, antigen binding proteins are administered in the form ofa composition comprising one or more additional components such as aphysiologically acceptable carrier, excipient or diluent. Optionally,the composition additionally comprises one or more physiologicallyactive agents, for example, a second IL-21 receptor-inhibitingsubstance, an anti-inflammatory substance, an anti-angiogenic substance,a chemotherapeutic substance, or an analgesic substance. In variousparticular embodiments, the composition comprises one, two, three, four,five, or six physiologically active agents in addition to an IL-21receptor binding antigen binding protein.

In one embodiment, the pharmaceutical composition comprise an antigenbinding protein of the invention together with one or more substancesselected from the group consisting of a buffer, an antioxidant such asascorbic acid, a low molecular weight polypeptide (such as those havingfewer than 10 amino acids), a protein, an amino acid, a carbohydratesuch as glucose, sucrose or dextrins, a chelating agent such as EDTA,glutathione, a stabilizer, and an excipient. Neutral buffered saline orsaline mixed with conspecific serum albumin are examples of appropriatediluents. In accordance with appropriate industry standards,preservatives such as benzyl alcohol may also be added. The compositionmay be formulated as a lyophilizate using appropriate excipientsolutions (e.g., sucrose) as diluents. Suitable components are nontoxicto recipients at the dosages and concentrations employed. Furtherexamples of components that may be employed in pharmaceuticalformulations are presented in Remington's Pharmaceutical Sciences, 16thEd. (1980) and 20th Ed. (2000), Mack Publishing Company, Easton, Pa.

Kits for use by medical practitioners include an IL-21receptor-inhibiting substance of the invention and a label or otherinstructions for use in treating any of the conditions discussed herein.In one embodiment, the kit includes a sterile preparation of one or moreIL-21 receptor binding antigen binding proteins, which may be in theform of a composition as disclosed above, and may be in one or morevials.

Dosages and the frequency of administration may vary according to suchfactors as the route of administration, the particular antigen bindingproteins employed, the nature and severity of the disease to be treated,whether the condition is acute or chronic, and the size and generalcondition of the subject. Appropriate dosages can be determined byprocedures known in the pertinent art, e.g. in clinical trials that mayinvolve dose escalation studies.

An IL-21 receptor inhibiting substance of the invention may beadministered, for example, once or more than once, e.g., at regularintervals over a period of time. In particular embodiments, an antigenbinding protein is administered over a period of at least a month ormore, e.g., for one, two, or three months or even indefinitely. Fortreating chronic conditions, long-term treatment is generally mosteffective. However, for treating acute conditions, administration forshorter periods, e.g. from one to six weeks, may be sufficient. Ingeneral, the antigen binding protein is administered until the patientmanifests a medically relevant degree of improvement over baseline forthe chosen indicator or indicators.

Particular embodiments of the present invention involve administering toa subject an antigen binding protein at a dosage of from about 1 ng ofantigen binding protein per kg of subject's weight per day (“1ng/kg/day”) to about 100 mg/kg/day, from about 500 ng/kg/day to about 50mg/kg/day, from about 5 μg/kg/day to about 20 mg/kg/day, and from about5 mg/kg/day to about 20 mg/kg/day to a subject. In additionalembodiments, an antigen binding protein is administered to adults onetime per week, two times per week, three times per week, four times perweek, five times per week, six times per week, or seven or more timesper week, to treat an IL-21 receptor mediated disease, condition ordisorder, e.g., a medical disorder disclosed herein. If injected, theeffective amount of antigen binding protein per adult dose may rangefrom, for example, 1-20 mg/m², or from about 5-12 mg/m². Alternatively,a flat dose may be administered; the amount may range from 1-300mg/dose. One range for a flat dose is about 20-30 mg per dose. In oneembodiment of the invention, a flat dose of 25 mg/dose is repeatedlyadministered by injection. If a route of administration other thaninjection is used, the dose is appropriately adjusted in accordance withstandard medical practices. One example of a therapeutic regimeninvolves injecting a dose of about 20-30 mg of antigen binding proteinto one to three times per week over a period of at least three weeks,though treatment for longer periods may be necessary to induce thedesired degree of improvement. For pediatric subjects (age 4-17), oneexemplary suitable regimen involves the subcutaneous injection of 0.4mg/kg, up to a maximum dose of 25 mg of antigen binding proteinadministered two or three times per week.

Particular embodiments of the methods provided herein involvesubcutaneous injection of from 0.5 mg to 10 mg, preferably from 3 to 5mg, of an antigen binding protein, once or twice per week. Anotherembodiment is directed to pulmonary administration (e.g., by nebulizer)of 3 or more mg of antigen binding protein once a week.

Examples of therapeutic regimens provided herein comprise subcutaneousinjection of an antigen binding protein once a week, at a dose of 1.5 to3 mg, to treat a condition in which IL-21 receptor signaling plays arole. Examples of such conditions are provided herein and are known inthe art. Administration of antigen binding protein can be continueduntil a desired result is achieved, e.g., the subject's symptomssubside. Treatment may resume as needed, or, alternatively, maintenancedoses may be administered.

Other examples of therapeutic regimens provided herein comprisesubcutaneous or intravenous administration of a dose of 1, 3, 5, 6, 7,8, 9, 10, 11, 12, 15, or 20 milligrams of an IL-21 receptor inhibitor ofthe present invention per kilogram body mass of the subject (mg/kg). Thedose can be administered once to the subject, or more than once at acertain interval, for example, once a day, three times a week, twice aweek, once a week, once every two weeks, once every three weeks, threetimes a month, twice a month, once a month, once every two months, onceevery three months, once every six months, or once a year. The durationof the treatment, and any changes to the dose and/or frequency oftreatment, can be altered or varied during the course of treatment inorder to meet the particular needs of the subject.

In another embodiment, an antigen binding protein is administered to thesubject in an amount and for a time sufficient to maintain theconcentration of the antigen binding protein at or above a desiredlevel, to maintain the amount, concentration, or other state of abiomarker at a desired level, or to induce an improvement, preferably asustained improvement, in at least one symptom or other indicator thatreflects the severity of the disorder that is being treated. Variousindicators that reflect the extent of the subject's illness, disease orcondition may be assessed for determining whether the amount and time ofthe treatment is sufficient. Such indicators include, for example,clinically recognized indicators of disease severity, symptoms, ormanifestations of the disorder in question. In one embodiment, animprovement is considered to be sustained if the subject exhibits theimprovement on at least two occasions separated by two to four weeks.The degree of improvement generally is determined by a physician, whomay make this determination based on signs, symptoms, biopsies, or othertest results, and who may also employ questionnaires that areadministered to the subject, such as quality-of-life questionnairesdeveloped for a given disease.

Combination Therapies

Treatments exist for most IL-21 receptor mediated diseases, even thoughmany of these treatments are effective only to a limited extent or foronly a subset of patients, and/or have substantial toxicities that limitpatient tolerance of treatment. The IL-21 receptor inhibitors describedherein can be combined with other existing therapies for IL-21receptor-mediated diseases.

In particular, an SLE patient can be treated concurrently with anothertherapy for SLE plus an IL-21 receptor-inhibitor such as an anti-IL-21receptor antibody as described herein. Existing therapies for SLEinclude glucocorticoids, such as prednisone, prednisolone, andmethylprednisolone, antimalarials such as hydroxychloroquine,quinacrine, and chloroquine, retinoic acid, aspirin and nonsteroidalanti-inflammatory drugs (NSAIDs), cyclophosphamide,dehydroepiandrosterone, mycophenolate mofetil, azathioprine,chlorambucil, methotrexate, tacrolimus, dapsone, thalidomide,leflunomide, cyclosporine, anti-CD20 antibodies such as rituximab, BLySinhibitors such as belimumab, anti-IFN-γ antibodies, and fusion proteinssuch as abatacept.

In other embodiments a patient suffering from an inflammatory boweldisease (IBD), such as Crohn's disease or ulcerative colitis, can beconcurrently treated with a therapy for IBD plus an anti-IL-21 receptorantibody as described herein. Existing therapies for IBD includesulfasalazine, 5-aminosalicylic acid and its derivatives (such asolsalazine, balsalazide, and mesalamine), anti-IFN-γ antibodies,anti-TNF antibodies (including infliximab, adalimumab, golimumab, andcertolizumab pegol), corticosteroids for oral or parenteraladministration (including prednisone, methylprednisone, budesonide, orhydrocortisone), adrenocorticotropic hormone, antibiotics (includingmetronidazole, ciprofloxacin, or rifaximin), azathioprine,6-mercaptopurine, methotrexate, cyclosporine, tacrolimus, andthalidomide.

In other embodiments, a patient suffering from rheumatoid arthritis canbe concurrently treated with a drug used for RA therapy plus ananti-IL-21 receptor antibody as described herein. Therapies forrheumatoid arthritis (RA) include non-steroidal anti-inflammatory drugs(NSAIDs) (such aspirin and cyclooxygenase-2 (COX-2) inhibitors), diseasemodifying anti-inflammatory drugs (DMARDs)(such as methotrexate,leflunomide, and sulfasalazine), anti-malarials (such ashydroxychloroquine), cyclophosphamide, D-penicillamine, azathioprine,gold salts, tumor necrosis factor inhibitors (such as etanercept,infliximab, adalimumab, golimumab, and certolizumab pegol), CD20inhibitors such as rituximab, IL-1 antagonists such as anakinra, IL-6inhibitors such as tocilizumab, inhibitors of Janus kinases (JAK) (suchas tofacitinib), abatacept, and glucocorticoids, among others.

In another embodiment, a patient suffering from sarcoidosis can beconcurrently treated with a drug used for sarcoidosis therapy plus ananti-IL-21 receptor antibody as described herein. Therapies forsarcoidosis include corticosteroids (may be topical or parenteral,depending on symptoms), salicylates (such as aspirin), anti-IFN-γantibodies, and colchicine. Choroquine has been reported to be helpfulwith cutaneous symptoms. Methotrexate, cyclophosphamide, azathioprine,and nonsteroidal anti-inflammatory drugs have also been used insarcoidosis. Various other treatment strategies can be helpful for someof the many different symptoms of sarcoidosis. For example, heartarrhythmias can be treated with antiarrhythmics or a pacemaker.Hypercalcemia can be treated with hydration, reduction in calcium andvitamin D intake, avoidance of sunlight, or ketoconazole. Skin lesionscan be treated with hydroxychloroquine, methotrexate, or thalidomide.

In another embodiment, a patient suffering from HLH can be concurrentlytreated with a drug used for HLH therapy plus an anti-IL-21 receptorantibody as described herein. Therapies for HLH include corticosteroids,intravenous immunoglobulin, IL-1 inhibiting agents such as anakinra,VP-16, etoposide, cyclosporine A, dexamethasone, various otherchemotherapeutics, bone marrow transplant or stem cell transplant,anti-IFN-γ antibodies, and antiviral and/or antibacterial agents.

EXAMPLES Example 1 Lead Candidate Selection

This example provides a method of screening for anti-IL-21 receptorantibodies.

Primary Screening

Two forms of human IL-21 receptor were used as antigens for XENOMOUSE™(Amgen Inc., Thousand Oaks, Calif.; transgenic mice engineered togenerate human antibodies) immunization. One form was a soluble humanFc-fusion (“IL-21R.Fc”) and the other was a full-length wild-type form.Both proteins were expressed using transient 293T cells. Hybridomas weregenerated using standard procedures using two pools of mice: IL-21R.Fcalone, designated as campaign #3 (harvest 5) and IL-21R/CHO stables,designated as campaign #4 (harvest 6). For campaign #3, the anti-IL-21Rspecific binders were identified by FMAT using full length wild-typeIL-21R expressed on the surface of stable CHO cells. For campaign #4,the antigen-specific binders were identified by FMAT using IL-21R/293transient cells. These primary screens resulted in the identification of692 (campaign #3) and 128 (campaign #4) antigen-specific binders. Thesepanels were then tested for binding to endogenous human IL-21R on RAMOScells by FACs. In this screen, 384 of the original 692 campaign #3binders and 58 of the original 128 campaign #4 binders showed somedegree of detectable binding to the RAMOS cells. The combined panel of442 IL-21R specific binders was advanced to additional characterizationscreens.

The primary selection criterion for antibodies with antagonist activitywas a flow cytometry-based receptor-ligand blocking assay using RAMOScells and labeled IL-21 ligand. The secondary selection criterion wascross-reactive binding to cyno IL-21R. This assay was also run by flowcytometry using full length cyno IL-21R transiently expressed on thesurface of 293Ts. These two selection criteria resulted in theidentification of 26 hybridomas of interest to advance to subcloning andscale up.

Three antibodies with functional antagonism and cross-reactive bindingto cyno IL-21R were subcloned as full IgG constructs and sequenceanalyzed. These antibodies were 34H7, which was derived from the solubleimmunogen, and 30G3 and 29G8, which were derived from the cell basedimmunogen.

Cloning and Sequence Analysis

The 30G3 light and heavy chain variable regions were PCR amplified fromindependent sub-clones derived from hybridomas and then DNA sequenced.The light chain variable region was cloned onto a kappa light constantregion. The gamma chain variable region was cloned onto an IgG2 constantregion. 30G3 was determined by sequence analysis to be composed of aVK3|L27|JK4 kappa light chain variable region and a VH4|4-59|JH4 gammavariable region. The heavy chain constant region (CH2) of 30G3 containedone N-linked glycosylation consensus site. The theoretical pI of thefull molecule was calculated to be 8.6 (with processed termini) andempirically determined to be 8.76. 34H7 and 29G8 were cloned andsequence analyzed in a similar manner

The table below lists salient features.

TABLE 1 Sequence Parameter 34H7 29G8 30G3 HC isotype huIgG2 huIgG2huIgG2 LC type huKappa huKappa huKappa Non germ Non germ Non germ Nongerm line framework line Germ line line Germ line line Germ lineresidues residue residue residue residue residue residue L 12 V_VH S 143T_VH A 48 P_VH R 30 S_VH T 102 A_VL M 80 I_VH H 94 S_VH V 2 I_VL V 98A_VH F 57 Y_VL S 108 R_VH N 94 S_VL S 90 T_VL L 103 V_VL Uncommonframework Same as above Same as above Same as above residues * Freq.VH/VL subtype ** 82.29%/18.75% 6.57%/5.68% 21.53%/55.36% VH/VL domainsubtype VH5|5-51/VK3|L2  VH3|3-33/VK1|L5  VH4|4-59/VK3|A27 ConsensusN-glycosylation HC: NST at 412 HC: NST at 412 HC: NST at 412 sites (CH2)(CH2) (CH2) Number of residues in HC 12 14 7 CDR3 Whole moleculetheoretical pI 8.55 8.67 8.6 (pI with processed N- and C- terminalresidues Immunogenicity (number 1 1 0 predicted agretopes) * Uncommonresidues are defined as being represented at less than 10% positionalfrequency within their respective family in the IMGT/Kabat database. **The subtype frequency within a family in the IMGT/Kabat database.

Example 2 Functional Screening

Several assays were used to test antibody activity. The primary assayfor ranking potency was the B/T cell co-culture described above becauseit involved inhibition of native IL-21 produced by T cells in closeproximity to responding B cells. Exogenous IL-21 assays were also usedto measure antibody potency. IL-21+CD40L stimulation was used tostimulate IgA from B cells. IL-21 alone was used to stimulate IFN-γproduction in CD8 T cells. Lastly, STAT3 phosphorylation was measured inIL-21-stimulated whole blood. For affinity measurements with recombinantIL-21R, both Biacore and KinExA were used. Affinity measurements werealso conducted on whole cells by flow cytometry, using anIL-21R-expressing cell line. The results of these assays for three mAbsare shown in Table 2. The values indicate concentration in pM(picomolar) at which IL-21 activity is inhibited by 50% (IC-50). Lowervalues represent more potent inhibition. For affinity measurements,lower values also represent higher affinity.

TABLE 2 Potency and affinity of IL-21R mAbs IC-50 (pM) CD8 T K_(D) (pM)B/T co-culture (IgA)¹ B cell (IgA)² (IFNγ)³ hu pSTAT3⁴ cyno pSTAT3Biacore Kinexa On Clone exp1 exp2 exp3 exp4 exp5 exp1 exp2 exp1 exp2 B TB T hu cyno hu cells⁵ 34H7 16 9 11 17 10 18 49 79 27 14 8 4 13 35 43 615 29G8 29 8 17 17 14 22 47 139 48 137 33 65 286 78 166 26 16 30G3 44 3124 24 19 58 31 203 35 36 10 9 33 16 78 15 33 Assay protocols ¹B/Tco-culture. Mitomicin C-treated human T cells were cultured with B cellsin anti-CD3 antibody pre-coated 96-well plates as described in Kuchen etal. (2007) J Immunol 179: 5886, incorporated herein by reference in itsentirety. Supernatants were collected for IgA ELISA on day 6. ²B cellIgA production. Negatively selected human peripheral blood B cells werecultured in vitro with IL-21 and CD40L. On day 6, supernatants werecollected for human IgG ELISA analysis. ³CD8 IFN-γ production. Purifiedhuman CD8 T cells were cultured with IL-21. IFN-γ was measured in thesupernatant on day 3. ⁴Whole blood pSTAT3 stimulation. Human orcynomolgus monkey whole blood was pre-incubated with IL-21R mAbstitrations at 37° C. for 1 hr and stimulated with IL-21. Cells werefixed, permeabilized and stained for pSTAT3 and cell surface markers.⁵Cell based K_(D) measurement. Ramos cells (Human Burkitt's lymphoma)were incubated with a titration of IL-21R mAbs and bound antibody wasdetected with anti-huIgG by flow cytometry.

Example 3 Cross-Competition Binding Assay

This example provides an assay for determining whether two antibodiescross-compete for binding to the extracellular domain of human IL-21receptor.

A cross-competition binding assay is performed using the BIACORE™ 3000instrument (Biacore International AB, Uppsala, Sweden and Piscataway,N.J.), following the manufacturer's protocols. A recombinant human IL-21receptor::FC chimera is immobilized onto the dextran layer of a CM5biosensor chip using amine coupling. Chips are prepared using 10 mMacetate buffer pH 5.0 as the immobilization buffer at a protein densityof 940 RU. Deactivation of unreacted N-hydroxysuccinimide esters isperformed using 1 M ethanolamine hydrochloride, pH 8.5. Purifiedantibodies or antibody fragments are diluted to a concentration of 50 nMin HBS-EP running buffer (0.01 M HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA,0.005% Polysorbate 20). A first anti-IL-21 receptor antibody is chosenand then injected across the flow cell for 600 seconds at a rate of 10μL/min. After the injection is complete, a second anti-IL-21 receptorantibody is chosen and injected across the same flow cell for 600seconds at a rate of 10 μL/min. (As a positive control forcross-competition, the first and second antibody can be the sameantibody. As a negative control for cross-competition, the firstantibody can be an antibody that does not specifically bind to humanIL-21 receptor.) The sensor surface is regenerated by a 12 secondinjection of 100 mM H₃PO₄ (25 μL/min). After regeneration, the secondantibody is now injected across the flow cell for 600 seconds at a rateof 10 μL/min. After the injection is complete, the first antibody isinjected across the same flow cell for 600 seconds at a rate of 10μL/min. The first and second antibodies are said to cross-compete forbinding to human IL-21 receptor if each reduces the binding of the otherin this assay by at least 80%.

What is claimed is:
 1. An isolated IL-21 receptor antigen bindingprotein, wherein said antigen binding protein comprises either: a. thelight chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or b. the heavy chainvariable domain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3; or c. the heavy chain variable domainand the light chain variable domain of antibody 10C2, 8B9, 8B9.13, 29G8,31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or d. a light chain variabledomain sequence that is at least 90%, 95%, 97%, or 99% identical to thelight chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or e. a heavy chainvariable domain sequence that is at least 90%, 95%, 97%, or 99%identical to the heavy chain variable domain sequence of antibody 10C2,8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or f. a lightchain variable domain sequence and a heavy chain variable domainsequence that each is at least 90%, 95%, 97%, or 99% identical to thelight chain variable domain sequence and the heavy chain variable domainsequence, respectively, of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2,31E7, 34H7, 30G3, or 37G3; or g. a light chain variable domain sequencethat differs at no more than 15, 12, 10, 8, 5, or 3 amino acid positionsfrom the light chain variable domain sequence of antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or h. a heavy chainvariable domain sequence that differs at no more than 15, 12, 10, 8, 5,or 3 amino acid positions from the heavy chain variable domain sequenceof antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or37G3; or i. a light chain variable domain sequence and a heavy chainvariable domain sequence that each differs at no more than 15, 12, 10,8, 5, or 3 amino acid positions from the light chain variable domainsequence and the heavy chain variable domain sequence, respectively, ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3;or j. a light chain variable domain sequence that is encoded by anucleic acid sequence that is at least 90%, 95%, 97%, or 99% identicalto the nucleic acid sequence encoding the light chain variable domainsequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7,30G3, or 37G3 as provided in FIG. 5; or k. a heavy chain variable domainsequence that is encoded by a nucleic acid sequence that is at least90%, 95%, 97%, or 99% identical to the nucleic acid sequence encodingthe heavy chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, as provided in FIG. 3; orl. a light chain variable domain sequence that is encoded by a nucleicacid sequence that is at least 90%, 95%, 97%, or 99% identical to thenucleic acid sequence encoding the light chain variable domain sequenceof antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or37G3, as provided in FIG. 5, and a heavy chain variable domain sequencethat is encoded by a nucleic acid sequence that is at least 90%, 95%,97%, or 99% identical to the nucleic acid sequence encoding the heavychain variable domain sequence of the same antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, as provided in FIG. 3; orm. a light chain variable domain sequence that is encoded by a nucleicacid sequence that hybridizes under moderately stringent, stringent, orhighly stringent conditions to the nucleic acid sequence encoding thelight chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 as provided in FIG. 5; or n.a heavy chain variable domain sequence that is encoded by a nucleic acidsequence that hybridizes under moderately stringent, stringent, orhighly stringent conditions to the nucleic acid sequence encoding theheavy chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 as provided in FIG. 3; or o.a light chain variable domain sequence that is encoded by a nucleic acidsequence that hybridizes under moderately stringent, stringent, orhighly stringent conditions to the nucleic acid sequence encoding thelight chain variable domain sequence of antibody 10C2, 8B9, 8B9.13,29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, as provided in FIG. 5, anda heavy chain variable domain sequence that is encoded by a nucleic acidsequence that hybridizes under moderately stringent, stringent, orhighly stringent conditions to the nucleic acid sequence encoding theheavy chain variable domain sequence of the same antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, as provided in FIG.3; or p. CDR1, CDR2, and CDR3 of the light chain variable domainsequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7,30G3, or 37G3; or q. CDR1, CDR2, and CDR3 of the light chain variabledomain sequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7,34H7, 30G3, or 37G3; or r. CDR1, CDR2, and CDR3 of the light chainvariable domain sequence, and CDR1, CDR2, and CDR3 of the heavy chainvariable domain sequence, of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5,29G2, 31E7, 34H7, 30G3, or 37G3; or s. light chain variable domain CDR1,CDR2, and CDR3 sequences that each differs at no more than 3, 2, or 1amino acid positions from the light chain variable domain CDR1, CDR2,and CDR3 sequences, respectively, of the light chain variable domainsequence of antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7,30G3, or 37G3; or t. heavy chain variable domain CDR1, CDR2, and CDR3sequences that each differs at no more than 3, 2, or 1 amino acidpositions from the heavy chain variable domain CDR1, CDR2, and CDR3sequences, respectively, of the heavy chain variable domain sequence ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3;or u. light chain variable domain CDR1, CDR2, and CDR3 sequences thateach differs at no more than 3, 2, or 1 amino acid positions from thelight chain variable domain CDR1, CDR2, and CDR3 sequences,respectively, of the light chain variable domain sequence of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3, andheavy chain variable domain CDR1, CDR2, and CDR3 sequences that eachdiffers at no more than 3, 2, or 1 amino acid positions from the heavychain variable domain CDR1, CDR2, and CDR3 sequences, respectively, ofthe heavy chain variable domain sequence of the same antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3; or v. a heavy chainvariable domain selected from the 31C5 group, the 29G2 group, the 31E7group, the 34H7 group, the 30G3 group, or the 37G3 group, of FIG. 12; orw. a light chain variable domain selected from the 10C2 group, the 8B9group, the 29G8 group, the 31C5 group, the 29G2 group, the 31E7 group,34H7 group, the 30G3 group, or the 37G3 group, of FIG. 13; or x. a heavychain variable domain selected from the 31C5 group, the 29G2 group, the31E7 group, the 34H7 group, the 30G3 group, or the 37G3 group, of FIG.12, and a light chain variable domain selected from the correspondinggroup of FIG. 13; or y. a light chain variable domain selected from the10C2 group, the 8B9 group, the 29G8 group, the 31C5 group, the 29G2group, the 31E7 group, 34H7 group, the 30G3 group, or the 37G3 group, ofFIG. 13, and a heavy chain variable domain selected from thecorresponding group of FIG. 12; or z. heavy chain CDR 1, 2, and 3sequences selected from one or more antibodies within the 31C5 group,the 29G2 group, the 31E7 group, the 34H7 group, the 30G3 group, or the37G3 group, of FIG. 12, and light chain CDR 1, 2, and 3 sequencesselected from one or more antibodies within the corresponding group ofFIG.
 13. 2. The IL-21 receptor antigen binding protein of claim 1,comprising: a. a heavy chain variable domain sequence disclosed in FIG.2; b. a light chain variable domain sequence disclosed in FIG. 4; c. aheavy chain variable domain sequence disclosed in FIG. 2 and a lightchain variable domain sequence disclosed in FIG. 4; d. the CDR1, CDR2,and CDR3 sequences of a heavy chain sequence disclosed in FIG. 2; e. theCDR1, CDR2, and CDR3 sequences of a light chain sequence disclosed inFIG. 4; f. the CDR1, CDR2, and CDR3 sequences of a heavy chain sequencedisclosed in FIG. 2 and the CDR1, CDR2, and CDR3 sequences of a lightchain sequence disclosed in FIG. 4; g. the heavy chain constant regiondisclosed in FIG. 7; h. the lambda light chain constant region disclosedin FIG. 7; i. the kappa light chain constant region disclosed in FIG. 7;j. the heavy chain constant region disclosed in FIG. 7 and either thelambda light constant region disclosed in FIG. 7 or the kappa lightchain constant region disclosed in FIG. 7; k. a heavy chain sequencedisclosed in FIG. 8; l. a light chain sequence disclosed in FIG. 9; m. aheavy chain sequence disclosed in FIG. 8 and a light chain sequencedisclosed in FIG. 9, wherein said heavy chain and said light chainsequence are from the same antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2,31E7, 34H7, 30G3, or 37G3; n. a heavy chain sequence disclosed in FIG.10; o. a light chain sequence disclosed in FIG. 11; p. a heavy chainsequence disclosed in FIG. 10 and a light chain sequence disclosed inFIG. 11, wherein said heavy chain and said light chain sequence are fromthe same antibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3,or 37G3.
 3. An isolated IL-21 receptor antigen binding protein thatcompetes for binding to a human IL-21 receptor with antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3.
 4. The isolatedIL-21 receptor antigen binding protein of claim 1, wherein said antigenbinding protein competes for binding to a human IL-21 receptor withantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3.5. The isolated IL-21 receptor antigen binding protein of claim 1,wherein said antigen binding protein comprises either: a. a light chainvariable domain that differs from the light chain variable domain ofantibody 10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3only in that one or more non-germline amino acid residues are replacedwith the corresponding germline residues; b. a heavy chain variabledomain that differs from the heavy chain variable domain of antibody10C2, 8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 only inthat one or more non-germline amino acid residues are replaced with thecorresponding germline residues; or c. a light chain variable domainthat differs from the light chain variable domain of antibody 10C2, 8B9,8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 only in that one ormore non-germline amino acid residues are replaced with thecorresponding germline residues, and a heavy chain variable domain thatdiffers from the heavy chain variable domain of the same antibody 10C2,8B9, 8B9.13, 29G8, 31C5, 29G2, 31E7, 34H7, 30G3, or 37G3 only in thatone or more non-germline amino acid residues are replaced with thecorresponding germline residues.
 6. The isolated IL-21 receptor antigenbinding protein of claim 1 comprising: a. a human antibody; b. ahumanized antibody; c. a chimeric antibody; d. a monoclonal antibody; e.a polyclonal antibody; f. a recombinant antibody; g. an antigen-bindingantibody fragment; h. a single chain antibody; i. a diabody; j. atriabody; k. a tetrabody; l. a Fab fragment; m. a F(ab′)2 fragment; n. adomain antibody; o. an IgD antibody; p. an IgE antibody; q. an IgMantibody; r. an IgG1 antibody; s. an IgG2 antibody; t. an IgG3 antibody;u. an IgG4 antibody; or v. an IgG4 antibody having at least one mutationin a hinge region that alleviates a tendency to form intra-H chaindisulfide bond.
 7. The isolated IL-21 receptor antigen binding proteinof claim 1 wherein said antigen binding protein inhibits binding ofIL-21 to IL-21 receptor.
 8. The isolated IL-21 receptor antigen bindingprotein of claim 1, wherein said antigen binding protein shows activityin the B/T co-culture assay, the B cell IgA production assay, the CD8IFN-γ production assay, or the whole blood pSTAT3 stimulation assay, ofExample
 3. 9. The isolated IL-21 receptor antigen binding protein ofclaim 8, wherein said antigen binding protein has a potency about equalto or greater than the potency shown in Table 2 for antibodies 34H7 or29G8 in the B/T co-culture assay, the B cell IgA production assay, theCD8 IFN-γ production assay, or the whole blood pSTAT3 stimulation assayof Example
 3. 10. An isolated polynucleotide comprising a sequence thatencodes the light chain, the heavy chain, or both of said isolated IL-21receptor antigen binding protein of claim 1 or of claim
 3. 11. Theisolated polynucleotide of claim 10, wherein said isolatedpolynucleotide comprises a light chain variable domain nucleic acidsequence of FIG. 5 and/or a heavy chain variable domain nucleic acidsequence of FIG.
 3. 12. A plasmid comprising said isolatedpolynucleotide of claim
 10. 13. The plasmid of claim 12, wherein saidplasmid is an expression vector.
 14. An isolated cell comprising saidisolated polynucleotide of claim
 10. 15. The isolated cell of claim 14,wherein a chromosome of said cell comprises said polynucleotide.
 16. Theisolated cell of claim 14, wherein said cell is a hybridoma.
 17. Theisolated cell of claim 14, wherein an expression vector comprises saidpolynucleotide.
 18. The isolated cell of claim 14, wherein said cell isa CHO cell.
 19. The isolated cell of claim 14, wherein said cell is abacterial cell.
 20. The isolated cell of claim 14, wherein said cell isan E. coli cell.
 21. The isolated cell of claim 14, wherein said cell isa yeast cell.
 22. The isolated cell of claim 14, wherein said cell is ananimal cell.
 23. The isolated cell of claim 14, wherein said cell is ahuman cell.
 24. A method of making an IL-21 receptor antigen bindingprotein, comprising incubating said isolated cell of claim 14 underconditions that allow it to express said antigen binding protein.
 25. Apharmaceutical composition comprising the IL-21 receptor antigen bindingprotein of claim 1 or of claim
 3. 26. A method of treating a conditionin a subject, comprising administering to said subject the IL-21receptor antigen binding protein of claim 1 or of claim 3, wherein saidcondition is treated or prevented by a reduction in IL-21 receptoractivity.
 27. The method of claim 26, wherein about 15 milligrams toabout 300 milligrams, about 30 milligrams to about 200 milligrams, about50 milligrams to about 150 milligrams, or about 75 milligrams to about125 milligrams of said antigen binding protein is administered to saidpatient.
 28. The method of claim 26, wherein said administration of saidantigen binding protein is repeated three times per day, twice per day,once per day, once every two days, once every three days, once per week,twice per week, three times per week, four times per month, three timesper month, twice per month, once per month, once every two months, onceevery three months, once every four months, once every six months, oronce per year.
 29. The method of claim 26, wherein a dose and afrequency of administration of said antigen binding protein are usedsuch as to maintain serum levels of said antigen binding protein in saidpatient at or above a desired level.
 30. The method of claim 26, whereinsaid condition is an infectious, inflammatory, or autoimmune condition.31. The method of claim 26, wherein said condition is Acquired ImmuneDeficiency Syndrome (AIDS), rheumatoid arthritis including juvenilerheumatoid arthritis, inflammatory bowel disease, ulcerative colitis,Crohn's disease, multiple sclerosis, Addison's disease, diabetes (typeI), epididymitis, glomerulonephritis, Graves' disease, Guillain-Barresyndrome, Hashimoto's disease, hemolytic anemia, systemic lupuserythematosus (SLE), lupus nephritis, myasthenia gravis, pemphigus,psoriasis, psoriatic arthritis, atherosclerosis, erythropoietinresistance, graft versus host disease, transplant rejection, autoimmunehepatitis-induced hepatic injury, biliary cirrhosis, alcohol-inducedliver injury, alcoholic cirrhosis, rheumatic fever, sarcoidosis,scleroderma, Sjogren's syndrome, a spondyloarthropathy, ankylosingspondylitis, thyroiditis, vasculitis, atherosclerosis, coronary arterydisease, or heart disease.
 32. The method of claim 26, furthercomprising administering to said subject a second treatment.
 33. Themethod of claim 32 wherein said second treatment is ananti-inflammatory, anti-infectious disease, or anti-autoimmune disordertreatment.
 34. The method of claim 26, wherein said antigen bindingprotein or pharmaceutical composition is administered subcutaneously orintravenously.